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Context: GH and IGF-I are known to promote breast carcinogenesis. Even if breast cancer (BC) incidence is not increased in female acromegalic patients, mortality is greater as compared with general population. Objective: The objective of the study was to evaluate whether GH/IGF-I excess might influence BC response to chemotherapy. Design: We evaluated GH and IGF-I effects on cell proliferation of a BC cell line, MCF7 cells, in the presence of doxorubicin (Doxo), frequently used in BC chemotherapy, and the possible mechanisms involved. Results: GH and IGF-I induce MCF7 cell growth in serum-free conditions and protect the cells from the cytotoxic effects of Doxo. GH effects are direct and not mediated by IGF-I because they are apparent also in the presence of an IGF-I receptor blocking antibody and disappear in the presence of the GH antagonist pegvisomant. The expression of the MDR1 gene, involved in resistance to chemotherapeutic drugs, was not induced by GH. In addition, c-fos transduction was reduced by Doxo, which prevented GH stimulatory effects. Pegvisomant inhibited basal and GH-induced c-fos promoter transcriptional activity. Autocrine GH action is ruled out by the lack of endogenous GH expression in this MCF7 cell strain. Conclusions: These data indicate that GH can directly induce resistance to chemotherapeutic drugs with a mechanism that might involve GH-induced early gene transcription and support the hypothesis that GH excess can hamper BC treatment, possibly resulting in an increased mortality. Growth hormone (GH) can directly induce chemoresistance, likely involving GH-induced early gene transcription. GH excess can hamper breast cancer treatment, possibly resulting in an increased mortality.

Somatostatin (SRIF) analogs interacting with SRIF receptor (SSTR) subtypes SSTR2 and SSTR5 reduce hormone secretion of pituitary adenomas, but their antiproliferative effects are still controversial. We investigated the in vitro effects of SRIF and SSTR-selective agonists interacting with SSTR1 (BIM-23926), SSTR2 (BIM-23120), SSTR5 (BIM-23206), or both SSTR2 and SSTR5 (BIM-23244) on alpha-subunit and chromogranin A secretion and on cell viability of 12 nonfunctioning pituitary adenomas (NFA) expressing SSTR1, SSTR2, and SSTR5, as assessed by RT-PCR. Treatment with SRIF or BIM-23206 did not modify alpha-subunit and chromogranin A secretion, which was significantly inhibited by BIM-23926, BIM-23120, and BIM-23244. SRIF and BIM-23120 did not influence cell viability, which was significantly promoted by BIM-23206 and BIM-23244 and reduced by treatment with BIM-23926. These results demonstrate that, in the selected NFA, the SSTR1-selective agonist inhibits secretory activity and cell viability, the SSTR2-selective agonist inhibits secretion but not cell viability, and the SSTR5-selective agonist does not influence secretion but promotes cell viability. These data can explain the lack of inhibitory effects of currently used SRIF analogs and suggest that drugs acting potently and preferentially on SSTR1 might be useful for medical treatment of NFA.

We investigated the 24-h profiles of the circulating levels of norepinephrine (NE) and epinephrine (E), blood pressure (BP), and heart rate in 14 acromegalic patients, before (A) and 3-6 months after transsphenoidal surgery (C-A, cured; A-A, active), and in 8 age-matched normal subjects (N). In addition, the responses of NE, E, PRA, and aldosterone to upright posture were investigated. No significant differences in the mean 24-h plasma NE and E levels were observed between either group of acromegalics and the N subjects. Analysis of the 24-h profiles indicated a statistically significant 24-h rhythm of both NE and E in N subjects. No evidence of a 24-h rhythm of plasma NE and E and BP was found in A patients. After surgery, a statistically significant 24-h rhythm of NE was detected in the patients with acrophase (13.54 and 13.45 h in C-A and A-A patients, respectively) and mesor (1019.8+/-45.1 and 1017.8+/-54.7 pmol/L in C-A and A-A patients, respectively) similar to those observed in N subjects (acrophase, 13.21 h; mesor, 942.3+/-42.5 pmol/L). After surgery, the plasma concentration of E clearly fluctuated throughout the 24 h in both C-A and A-A patients, even if cosinor analysis failed to reveal a 24-h significant rhythm. A statistically significant 24-h rhythm of BP was restored only in C-A patients. The mean 24-h heart rate was slightly, but significantly (P

There is evidence that withdrawal of SRIH infusion in man promotes a rebound GH response that allegedly has been proposed to be related to the function of GHRH-producing neurons. In the present study we have evaluated whether a reduction in endogenous GHRH activity contributes to the decreased GH secretion of the elderly. Sixteen young (8 women, aged 23–32 yr, and 8 men, aged 18–27 yr) and 13 elderly (8 women, aged 65–82 yr, and 5 men, aged 65–70 yr) healthy subjects volunteered to participate in this investigation. Each subject was tested on 2 separate occasions: 1) a 90-min iv infusion of SRIH was given in 50 mL 0.9% saline delivered at a rate of 9 μg/kg·h; and 2) a 90-min iv infusion of isovolumetric amounts of 0.9% saline was given. Plasma GH levels were determined before and up to 180 min after SRIH or saline infusion, whereas plasma insulin-like growth factor I, estradiol, and testosterone levels were measured in basal samples. In elderly women, the mean maximum (Δ) GH peak (2 ± 0.7 μg/L) after with...

To investigate the influence of the sympathoadrenomedullary system on the modulation of the circulating levels of calcitonin gene-related peptide (CGRP), the effects of epinephrine (E) and norepinephrine (NE) were studied in 8 normal subjects (4 females and 4 males). The mean basal levels of CGRP in normal subjects were 10.2 +/- 1 pmol/l. After the infusion of E (20 ng/kg per min for 30 min), a significant rise (P < 0.005) in plasma CGRP levels was observed with the expected increases in systolic blood pressure (BP), heart rate (HR) and plasma renin activity (PRA), and decrease in diastolic BP, whereas plasma aldosterone (PA) levels did not significantly change. The infusion of NE (40 ng/kg per min for 30 min) induced an increase in systolic and diastolic BPs, whereas it failed to modify CGRP, HR, PA and PRA. Our data demonstrate that the sympathoadrenomedullary system may modulate CGRP release in man perhaps via the beta-adrenergic pathway. It is likely that the modifications of plasma CGRP levels may be part of the acute vasal response to E.

Recently we demonstrated the inhibitory action on Growth Hormone (GH) secretion of an opioid heptapeptide, deltorphin (DT), that is highly selective in binding delta-opioid receptors. To investigate the possible mechanism leading to the decrease in GH secretion by specific activation of delta-opioidergic pathway in man, we compared, in normal subjects, the effect of DT on GH secretion responses to two different GH secretagogues, namely arginine (ARG) and galanin (GAL). DT completely blunted the GH response to ARG, whereas it attenuated the GH response to GAL, but not at a statistically significant level. We suggest that the specific activation of delta-opioid receptors in man may exert an inhibitory influence on GH secretion principally by modulating endogenous hypothalamic somatostatin (SRIH) release.

The occurrence and extent of a circadian rhythm in the circulating concentrations of atrial natriuretic peptide (ANP) are still matters of controversy. Only a few data are available in humans relating the time structure of plasma ANP levels with the circadian patterns of other hormones and cardiovascular variables. In a group of hospitalized normal volunteers (six men and four women, 16-76 years old), and in a group of hospitalized hypertensives (seven men and three women, 18-76 years old), we investigated the circadian variability of ANP and its temporal relationship with the circadian rhythms of blood pressure (BP) and heart rate (HR), and plasma renin activity (PRA), plasma aldosterone (PA) and plasma cortisol (PC) levels, by using a chronobiological inferential statistic method. At the end of a synchronizing period of 1 week (the diet and daily schedule were standardized), the subjects underwent automatic BP and HR monitoring, and blood sampling for 24 h. A statistically significant mean circadian rhythm was demonstrated for ANP, BP, HR, PRA, PA and PC in both normal and hypertensive subjects. The mean circadian acrophase of ANP (calculated to occur at around 04.00 h) anticipated the corresponding acrophases of the other hormones; BP and HR rhythms appeared to be in antiphase with ANP rhythm, i.e. the peak of BP and HR rhythms more or less coincided with the trough in ANP rhythm. A significant increase in the daily levels (assessed by the circadian mesor) of ANP was present in hypertensive subjects when compared with normal controls. In essential hypertension the circadian rhythm of ANP was set at higher circulating levels, but otherwise it was similar to the circadian rhythm found in normals. ANP mesors correlated significantly with renin and aldosterone mesors in normal subjects but not in hypertensive patients. ANP appears to anticipate awakening in its circadian periodic rise. On the basis of the considerable acrophase asynchronism, it seems possible to exclude any causal relations between the periodic changes of ANP and the rhythmic fluctuations of the other hormones that we studied. In contrast, important relations may be hypothesized between ANP levels and BP and HR values, on the basis of their antiphase rhythms.

Medullary thyroid carcinoma (MTC) is a rare tumor originating from thyroid parafollicular C cells. We previously demonstrated that somatostatin (SRIH) reduces cell growth in the human MTC cell line, TT, which expresses all SRIH receptor (SSTR) subtypes and responds differently to selective SSTR agonists.To clarify the possible effects of SRIH analogs on hormone secretion and proliferation in MTC primary cultures, we evaluated SSTR expression and assessed the in vitro effects on calcitonin (CT) and chromogranin A secretion as well as cell viability of SRIH analogs interacting with SSTR1, SSTR2, and SSTR5.Thirty-five patients affected by MTC were recruited from 2003 to 2005. After total thyroidectomy, the samples were examined for CT, chromogranin A, and SSTR expression by RT-PCR. Primary cultures were developed and tested with SRIH analogs interacting with SSTR1, SSTR2, and SSTR5.We selected 18 MTC tumor samples, expressing SSTR1, SSTR2, and SSTR5. Two different groups were identified according to CT secretion inhibition by the clinically available SRIH analog, lanreotide. In the responder group, CT secretion was reduced by compounds interacting with SSTR1, SSTR2, and SSTR5, whereas cell viability was not affected. On the other hand, in the nonresponder group, CT secretion was reduced by the SSTR1 selective agonist, whereas cell viability was inhibited by SSTR2 selective agonists.Our data suggest that SRIH analogs might be useful in medical therapy of MTC because they could have antiproliferative effects despite the lack of antisecretory activity and vice versa.

A 29-yr-old woman presented with acromegaly, pituitary gland enlargement, and an isolated pulmonary mass of 3.3 cm in diameter, which displayed a very high tracer uptake after OctreoScan. Plasma GHRH levels were markedly elevated. The patient underwent left lung upper lobectomy, and histopathology disclosed a bronchial atypical carcinoid. The tissue was examined for somatostatin (SRIH) receptor subtypes (SSTRs) 1-5 expression by RT-PCR. Cultured tumor cells were treated with SRIH, lanreotide (BIM-23014), or SRIH analogs selective for SSTR2 (BIM-23120), SSTR5 (BIM-23206), or SSTR1 (BIM-23926). GHRH was measured in the medium after 6 h, and cell viability was assessed after 48 h. RT-PCR analysis showed expression of SSTR1, -2, and -5. GHRH secretion was significantly reduced by SRIH (-50%), Lan (-35%), as well as by the SSTR2, SSTR5, and SSTR1 selective agonists (-55, -75, and -20%, respectively), whereas cell viability was not affected. Our data show SSTR expression in a GHRH-secreting bronchial carcinoid and provide evidence that, in vitro, selective SSTR activation differently inhibit ectopic GHRH secretion. These findings suggest that SSTR-specific SRIH analogs may be useful in the medical therapy of GHRH-secreting bronchial carcinoids.

Dopamine (DA) and somatostatin (SRIF) receptor agonists inhibit growth hormone (GH) secretion by pituitary adenomas. We investigated DA subtype 2 receptor (DR2) and SRIF receptor (sst) subtypes 2 and 5 expression in 25 GH-secreting pituitary adenomas and tested in primary culture the effects on GH and prolactin (PRL) secretion of sst agonists selectively interacting with sst2 (BIM-23120), sst5 (BIM-23206), and sst2 and sst5 (BIM-23244). All adenomas expressed sst2; eight adenomas expressed both sst5 and DR2, eight sst5 but not DR2, and eight DR2 but not sst5. One tissue lacked expression of DR2 and sst5. GH secretion was inhibited by BIM-23120 in all samples, while it was reduced by BIM-23206 only in adenomas not expressing DR2. BIM-23120’s inhibitory effects correlated with sst2 and DR2 expression, whereas DR2 expression correlated inversely with BIM-23206 inhibitory effects on GH secretion. In seven mixed GH-/PRL-secreting pituitary adenomas, PRL secretion was inhibited in sst5-expressing tumors by BIM-23206, but not by BIM-23120. BIM-23244 reduced PRL secretion only in adenomas expressing sst2, sst5 and DR2. sst5 and DR2 expression correlated directly with BIM23206 inhibitory effects on PRL secretion. Our results suggest that adenomas expressing DR2 are less likely to respond to clinically available SRIF analogs in terms of GH secretion inhibition. Therefore, drugs interacting also with DR2 might better control secretion of pituitary adenomas.

Somatostatin (SRIF) analogs interacting with SRIF receptor subtype (SSTR) 2 and SSTR5 are known to reduce secretion in GH-secreting pituitary adenomas. We investigated the effects of SRIF and a SSTR1 selective agonist, BIM-23926, on GH and prolactin (PRL) secretion and cell viability in primary cultures deriving from 15 GH- and PRL-secreting adenomas expressing SSTR1. Quantitative RT-PCR showed SSTR1 mRNA mean levels of 6 +/- 2.2 x 10(4) molecules/ microg reverse-transcribed total RNA. SSTR2 and SSTR5 were frequently expressed (93.3%), on the contrary of SSTR3 (53.3%) and SSTR4 (6.7%). GH secretion was significantly reduced by SRIF and BIM-23926 (45 +/- 8.6% and 32 +/- 18.1% inhibition, respectively) as well as PRL secretion (16.1 +/- 4% and 19.7 +/- 3.5% inhibition, respectively). After treatment with SRIF and BIM-23926, cell viability was significantly reduced by 17.5 +/- 5% and 20 +/- 3.9%, respectively. SSTR1 mRNA levels correlated with the degree of GH and PRL secretion inhibition. These results demonstrate that SSTR1 selective activation inhibits hormone secretion and cell viability in GH- and PRL-secreting adenomas in vitro and suggest that SRIF analogs with affinity for SSTR1 may be useful to control hormone hypersecretion and reduce neoplastic growth of pituitary adenomas.

Testosterone (T) is known to affect the growth hormone (GH) axis. However, the mechanisms underlying the activation of GH secretion by T still remain to be clarified. Available data in animals and humans have shown that withdrawal of somatostatin (SRIH) infusion induces a GH-releasing hormone (GHRH)-mediated rebound release of GH, and there is accumulating evidence that SRIH infusion withdrawal may be a useful test to probe the GHRH function in vivo. With the aim of investigating whether the stimulatory effect of androgens on GH release in man could be accounted for by activation of the hypothalamic GHRH tone, we evaluated the plasma GH response to SRIH withdrawal in 10 patients aged 29.6 ± 2.4 years (mean ± SEM), diagnosed with hypergonadotropic hypogonadism, before and after a 6-month replacement therapy with T enanthate (250 mg every 3 weeks, i.m.), and in 10 healthy men, aged 26.7 ± 2.8 years. To verify whether the modulation of GH secretion by T could also be mediated through changes in SRIH tone and/or pituitary releasable pool, we examined GH secretory responses to combined GHRH and L-arginine (ARG) in the same individuals. Basal plasma concentrations of GH (0.48 ± 0.11 µg/l) and IGF-I (23.79 ± 1.83 nmol/l) were significantly lower in untreated hypogonadal patients than in healthy men, and significantly increased after T replacement therapy (GH 1.13 ± 0.28 µg/l; IGF-I 28.71 ± 1.46 nmol/l). The mean ΔGH peak after SRIH withdrawal recorded in untreated hypogonadal men (2.65 ± 0.86 µg/l) was significantly (p < 0.05) lower than that observed in healthy men (6.53 ± 1.33 µg/l) and significantly increased after T replacement therapy (5.52 ± 1.25 µg/l). The GH responses to GHRH combined with ARG (a functional SRIH antagonist) were not significantly different between healthy men and untreated hypogonadal patients, and were not significantly affected by T treatment. Plasma T and estradiol (E2) levels significantly correlated with ΔGH peak after SRIH withdrawal in healthy men and in T-treated hypogonadal patients, whereas in untreated patients they did not. No significant correlation was found between GH areas under the curve after GHRH + ARG test and T and E2 plasma levels in either healthy men or in hypogonadal patients (both before and after T replacement). These findings are consistent with the view that in humans the stimulatory action of T on the GH axis appears to be mediated at the hypothalamic level primarily by promoting GHRH function.

Neurohumoral factors may contribute to cardiovascular changes associated with vasovagal syncope (VVS). Galanin (GAL) is a neuropeptide, widely distributed in the central and peripheral nervous systems, that interacts with both sympathetic and vagal systems as well as with neurotransmitters, such as serotonin. We investigated the changes in plasma GAL and catecholamine levels during head-up tilt (HUT) test in patients with recurrent VVS. Twenty-two patients (11 women, aged 33.1 ± 4.2 years) with a history of VVS and 10 healthy subjects (5 women, aged 38.0 ± 5.8 years) underwent HUT test (60°, 45 minutes). GAL and catecholamine plasma levels were measured in the supine position, during HUT and, in patients with positive response, at presyncope, syncope, and after recovery of consciousness. Thirteen patients developed syncope during HUT, whereas no healthy subjects had a positive response. In healthy subjects, GAL did not change during HUT. By contrast, in patients with a history of VVS and a negative response to tilting (no syncope), GAL significantly (P

OBJECTIVE: Menopause is associated with critical changes in the cardiovascular system, and the possible effect of hormonal replacement therapy (HRT) on these changes is under investigation. The aim of our study was to evaluate in postmenopausal women the effects of HRT and clonidine on the response of plasma calcitonin gene-related peptide (CGRP) and plasma atrial natriuretic peptide (ANP) to the upright posture test and the saline infusion test respectively. METHODS: CGRP and ANP levels were measured with specific radioimmunological assays and expressed in pmol/l (means +/- S.E.M). DESIGN: Postmenopausal women (age 46-53 years) (n = 18) were studied before and after 3 months of HRT (n = 13) or clonidine treatment (n = 5). RESULTS: After HRT or clonidine treatment plasma CGRP levels (14.9 +/- 1.6 and 15.9 +/- 3.8 pmol/l) were significantly higher than before (9.8 +/- 0.6 and 10.5 +/- 1.6 pmol/l) (P < 0.01). The assumption of upright posture caused no change in plasma CGRP levels before treatment, while after HRT, but not after clonidine treatment, an increase in plasma CGRP levels was observed (P < 0.01 at 5 and 20 min). Basal plasma ANP levels significantly decreased after both HRT and clonidine treatment (P < 0.01). In untreated women the saline infusion test did not induce any change in plasma ANP levels; a significant response to the test was restored after HRT but not after clonidine treatment (P < 0.01 at 90 and 120 min). CONCLUSIONS: The results show that some of the adaptive responses modified by menopausal changes are restored by HRT but not clonidine treatment, suggesting a modulatory role for sex steroid hormones in cardiovascular function and salt and water balance.

The neuropeptide galanin (GAL) is widely distributed in the central and peripheral nervous systems where it often coexists with catecholamines and acetylcholine. Recently we have reported that human GAL (hGAL) in man depresses the release of norepinephrine (NE) and the responses to both assumption of upright posture and insulin-induced hypoglycemia. To gain an insight into the action of hGAL on sympathetic nervous system activity in man, we investigated the effects of a 60-min infusion (80 pmol/kg/min) of hGAL or saline on the release of NE, epinephrine (E) and pancreatic polypeptide (PP) induced by an acetylcholinesterase inhibitor, pyridostigmine bromide (PD), in nine healthy volunteers. PD (120 mg orally) induced a significant rise in plasma concentrations of NE (1.6 +/- 0.04 vs. 1.08 +/- 0.06 nmol/l), E (0.34 +/ 0.05 vs. 0.12 +/- 0.04 nmol/l) and PP (178.06 +/- 33 vs. 37.57 +/- 7.35 pmol/l), whilst it significantly reduced heart rate (HR; 61 +/- 2 vs. 71 +/- 4 beats/min). Changes in plasma levels of PP were determined as an indirect measure of amplification of endogenous cholinergic activity produced by PD. Administration of hGAL blunted the release of NE and PP evoked by PD. The mean (+/- SEM) area under the curve produced by PD of NE (50.05 +/- 3.97 nmol/l.90 min) and PP (8,692.87 +/- 1,724 pmol/l.90 min) was significantly (p0.001) reduced by hGAL infusion (2.65 +/- 1.57 nmol/l.90 min and 248.1 +/- 148 pmol/l.90 min, for NE and PP, respectively). hGAL failed to affect significantly the E release evoked by PD. hGAL was able to enhance HR significantly (104 +/- 5 vs. 69 +/- 3 beats/min), and completely prevented the PD-induced slowing of HR. Both PD and hGAL did not alter supine systolic and diastolic blood pressure. We conclude that hGAL significantly reduces the release of NE and PP stimulated by PD-induced enhancement of cholinergic activity. These findings are consistent with a functional interrelationship between GAL and the cholinergic system in man, and may suggest the participation of a cholinergic pathway in the galaninergic modulation of the autonomic nervous system.

degli Uberti EC, Ambrosio MR, Bondanelli M, Trasforini G, Valentini A, Rossi R, Margutti A, Campo M. Effect of human galanin on the response of circulating catecholamines to hypoglycemia in man. Eur J Endocrinol 1995;133:723–8. ISSN 0804–4643 Human galanin (hGAL) is a neuropeptide with 30 amino acid residues that has been found in the peripheral and central nervous system, where it often co-exists with catecholamines. In order to clarify the possible role of hGAL in the regulation of sympathoadrenomedullary function, the effect of a 60 min infusion of hGAL (80 pmol·kg−1 · min−1) on plasma epinephrine and norepinephrine responses to insulin-induced hypoglycemia in nine healthy subjects was investigated. Human GAL administration significantly reduced both the release of basal norepinephrine and the response to insulin-induced hypoglycemia, whereas it attenuated the epinephrine response by 26%, with the hGAL-induced decrease in epinephrine release failing to achieve statistical significance. Human GAL significantly increased the heart rate in resting conditions and clearly exaggerated the heart rate response to insulin-induced hypoglycemia, whereas it had no effect on the blood pressure. We conclude that GAL receptor stimulation exerts an inhibitory effect on basal and insulin-induced hypoglycemia-stimulated release of norepinephrine. These findings provide further evidence that GAL may modulate sympathetic nerve activity in man but that it does not play an important role in the regulation of adrenal medullary function. Ettore C degli Uberti, Chair of Endocrinology, University of Ferrara, Via Savonarola 9, I-44100 Ferrara, Italy

To examine the role of delta-opioid receptors in the regulation of the sympathoadrenomedullary system, the effects of the highly selective delta-opioid receptor agonist deltorphin (DT) on plasma catecholamine responses to insulin-induced hypoglycemia (IIH) and cold pressor test (CPT) have been investigated in normal subjects in two separate studies. DT failed to modify basal plasma levels of both norepinephrine (NE) and epinephrine (E). DT completely suppressed the IIH-evoked elevation of NE, whereas it attenuated the E response by 20%, with the DT-induced decrease in E release failing to achieve statistical significance. DT completely blocked the release of both NE and E elicited by CPT. We conclude that specific delta-opioid receptor stimulation exerts an inhibitory effect on NE release induced by both IIH and CPT. These findings provide evidence that delta-opioid receptors may influence the autonomic sympathetic reactivity.

Calcitonin gene-related peptide (CGRP) has positive chronotropic and inotropic effects in animals and humans, and produces the most potent vasodilation known for an endogenous peptide. Yet, a physiological role for CGRP in the regulation of vascular tone and blood pressure has not been demonstrated. We studied the effects of 1) assumption of the upright position and 2) iv infusion of angiotensin-II (sequential doses of 8, 16, and 32 ng/kg.min, each dose for 20 min) in eight normal subjects (four men). Serial venous blood samples were taken to determine the plasma CGRP, epinephrine, norepinephrine, and aldosterone levels and PRA. Blood pressure and heart rate were continuously monitored at the finger with a Finapres 2300 instrument. After assumption of the upright posture, a quick rise in plasma CGRP levels was observed together with the expected increases in plasma norepinephrine and aldosterone and PRA. A transient increment was also observed for diastolic blood pressure and heart rate. Angiotensin-II infusion caused dose-dependent increases in plasma CGRP and aldosterone concentrations, already significant at the lowest infusion rate and parallel with the blood pressure rise. Plasma catecholamines significantly increased only at higher infusion rates. Our data demonstrate that modifications of plasma CGRP concentrations are part of the normal response to postural and vasomotor changes. These findings suggest a physiological role for CGRP in regulation of the peripheral vascular tone and possibly blood pressure in man.

To investigate the role of delta-opioid receptors in the modulation of growth hormone (GH) secretion, we compared in normal subjects the effect of the highly selective delta-opioid receptor agonist Deltorphin (DT) on the GH secretion responses to pituitary (GH-releasing hormone, GHRH)- and hypothalamic (insulin-induced hypoglycemia, IIH)-mediated stimuli. DT blunted the GH response to IIH, whereas it had no effect on the GH response to GHRH. It is concluded that in man DT-induced activation of delta-opioid receptors exerts an inhibitory action on hypoglycemia-stimulated GH secretion. Based on the lack of an effect of DT on the GH response to GHRH, we suggest that DT may modulate the secretion of GH through suprapituitary mechanisms.

To assess the existence of an altered circulating pattern of calcitonin gene-related peptide (CGRP) in hypertension.The 24 h variation in plasma CGRP was measured and compared in 10 patients affected by uncomplicated essential hypertension and in nine age- and sex-matched healthy volunteers. The diurnal variations in blood pressure, atrial natriuretic peptide (ANP), plasma renin activity (PRA), plasma aldosterone and plasma cortisol were also assessed.Recumbency studies were performed under standardized, drug-free conditions beginning at 0800 h. Venous samples were drawn every 4 h for 24 h and hormone levels were assessed with specific radioimmunoassays. The blood pressure was measured every 15 min with a SpaceLabs 90207 monitor.The mean 24-h plasma CGRP concentrations were significantly lower in the hypertensive group than in the control group. In both groups a circadian rhythm was present with the same pattern, but at a lower level in hypertension. A temporal sequence starting with the nocturnal rise in plasma CGRP concentrations and progressing with the elevations of ANP, PRA, and plasma aldosterone and cortisol was apparent in both groups. The nocturnal rise in the CGRP and ANP concentrations coincided with the blood pressure and the heart rate falls.Our data show that CGRP is lower than normal but maintains its circadian variability and its relationship with the diurnal variations in blood pressure and other hormones known to be active on the cardiovascular system.

To determine the role of delta-opioid receptors in the modulation of hypothalamic-pituitary-adrenal activity, we studied in normal subjects the effect of the highly selective delta-opioid receptor agonist deltorphin (DT) on the secretion of ACTH, cortisol, and arginine vasopressin in response to insulin-induced hypoglycemia. In an attempt to clarify the site of opiate modulation of ACTH secretion, we also studied in normal subjects the effect of DT on the ACTH response to ovine CRH-41. DT blunted the ACTH, cortisol, and arginine vasopressin responses to insulin-induced hypoglycemia, whereas it had no effect on the ACTH and cortisol responses to CRH. We conclude that DT-induced activation of delta-opioid receptors exerts an inhibitory influence on hypoglycemia-stimulated ACTH secretion. Based on the lack of an effect of DT on the ACTH response to CRH, we postulate that DT may modulate the secretion of ACTH through suprapituitary mechanisms.

Calcitonin gene-related peptide (CGRP) is known to exert potent cardiovascular effects and is presumed to participate in the neural control of circulation and blood flow. It has been assayed in many physiological and disease conditions, yet virtually nothing is known of the normal fluctuations in its circulating levels. We have studied the variability throughout a 24-h period of plasma concentrations of CGRP in eight recumbent healthy volunteers (four men and four women, 25-37 yr old), after careful standardization of their daily diet and routine schedules. A correlation with the circadian rhythms of blood pressure (BP), heart rate (HR), and plasma aldosterone (PA), PRA, plasma cortisol (PC), and atrial natriuretic peptide (ANP) was also made. Plasma CGRP concentrations ranged from a mean peak value of 18.1 +/- 1.5 pmol/L to a mean lowest value of 11.7 +/- 0.4 pmol/L (P less than 0.05). The mean circadian acrophase of CGRP (calculated by cosinor analysis to occur at 2314 h) anticipated the corresponding acrophases of the other hormones (0122, 0528, 0809, and 0840 h for ANP, PRA, PA, and PC, respectively). Instead, BP and HR rhythms seemed to be antiphasic with the ANP rhythm (calculated acrophases occurred at 1356, 1339, and 1314 h for systolic BP, diastolic BP, and HR, respectively). Our data demonstrate that, like many other hormones, CGRP circulates in plasma with a circadian rhythm. There seems to be a temporal sequence starting with the nocturnal rise in plasma CGRP concentrations and progressing with the ensuing elevations of ANP, PRA, PA, and PC, whereas BP and HR are kept to their lowest values. These findings are in favor of a physiological role of CGRP in the complex regulation of BP homeostasis.

The action of somatostatin (SRIH) on 3H-thymidine (thy) incorporation and on c-myc and thyroglobulin RNA levels in a suspension of follicles from normal and goitrous human thyroid was examined. SRIH, at 10(-7) M concentration, inhibited basal thy incorporation (maximally by 4 h lasting for up 24 h), which effect was greater in goiter than in normal thyroid and was also detected in growing adherent epithelial cells. Moreover, in a follicle suspension SRIH prevented TSH-stimulated thy incorporation, both in normal and in goitrous thyroid. Basal expression of c-myc RNA was not affected by SRIH in either tissue, whereas the TSH-stimulated c-myc RNA level was significantly reduced in goiter. No effect of SRIH was observed on basal or TSH-stimulated thyroglobulin RNA levels. SRIH did not alter basal cAMP concentrations in normal or goitrous follicles, but it significantly reduced TSH-stimulated cAMP accumulation both in normal thyroid and in goiter. Overall, our data indicate a direct inhibitory action of SRIH on growth, but not on differentiation, of human thyroid, probably by a mechanism not entirely cAMP dependent.

In this study we investigated the effect of intravenous infusion of angiotensin II (AII) on plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels in fertile healthy women examined both in the middle follicular phase (MFP) and in the middle luteal phase (MLP). As expected, AII induced a significant increase in blood pressure and plasma aldosterone concentration. In MFP, plasma FSH and LH levels did not show any significant change after AII infusion, if compared to both saline and preinfusion basal values. In MLP, AII significantly increased plasma LH (p less than 0.02 vs. baseline values and p less than 0.01 vs. placebo values), but not plasma FSH. The area under the curve during AII infusion resulted significantly higher than during placebo infusion (p less than 0.001). Therefore, these data demonstrate that peripherally injected AII at pressive dose produces an increase in plasma LH levels in normal women on luteal phase when the circulating concentrations of both estradiol and progesterone are high. The study suggests that AII may have a stimulatory role in the regulation of LH secretion, but this role is closely related to the gonadal steroid plasma levels.

We studied the response of atrial natriuretic peptide to the hemodynamic and renin-aldosterone variations occurring in four patients who developed cardiac tamponade, either occurring in idiopathic fashion in one or secondary to metastatic involvement of the pericardium in three. Right atrial pressure, heart rate and arterial blood pressure were monitored and serial blood samples were taken before and over three hours after pericardiocentesis. During cardiac tamponade, normal levels of atrial natriuretic peptide (mean +/- SEM: 54 +/- 7.4 pg/ml) were observed in the plasma despite increased right atrial pressure (23 +/- 3.8 cm H2O) and heart rates (98 +/- 4.4). Removal of pericardial fluid (540 to 1160 ml) was associated at first with a 200% increase in plasma concentrations of atrial natriuretic peptide (108 +/- 8.8 pg/ml; P less than 0.001), then with a gradual decline toward normal levels, simultaneous with the normalization of right atrial pressure and heart rate. Activity of renin and concentrations of aldosterone in the plasma were increased during tamponade and returned gradually to normal after pericardiocentesis (3.8 +/- 0.9 to 1.2 +/- 0.3 ng/ml/h and 20 +/- 4.2 to 9 +/- 3.2 ng/dl, respectively; P less than 0.01). These data confirm that atrial strain, not intracavitary pressure in itself nor heart rate, is the main determinant of the acute release of atrial natriuretic peptide, which is associated with a suppressing effect on the renin-aldosterone system. In addition, our data indicate that secretion of atrial natriuretic peptide during cardiac tamponade is not stimulated by secondary hyperaldosteronism.

The intravenous (IV) infusion of angiotensin II (AII) was administered to seven healthy male volunteers in a randomized placebo-controlled study. As expected, All induced a significant increase in blood pressure and plasma aldosterone concentrations. All caused a significant increase in corticotropin (ACTH) and growth hormone (GH) release, but had no effect on the release of thyrotropin (TSH) and prolactin (PRL). These findings suggest that peripherally circulating All might influence ACTH and GH secretion in humans.

Placebo controlled trials have generally been used in order to evaluate the antihypertensive efficacy of drugs. There is some evidence, though, that blood pressure might not be influenced by placebo. Noninvasive devices for automatic blood pressure monitoring are likely to provide a better assessment of blood pressure response to drugs, as well as to different physiologic and pathologic conditions, than the traditional sphygmomanometric devices. The aim of this study was to investigate the effect of placebo on blood pressure recorded automatically and noninvasively. For this purpose, a chronobiologic approach to the collection, evaluation and interpretation of data seemed most appropriate.A group of 12 patients with a clinical diagnosis of essential hypertension underwent automatic blood pressure monitoring in hospital for 4 days. Measurements were taken every 15 min by an oscillometric instrument with an automatically inflated cuff. After a washout period during which the patients received no treatment, pressure recording was undertaken under basal conditions for 2 days. On the third and fourth days of study, the patients received 2 tablets of placebo, one at 10a.m. and one at 10p.m. In each patient a highly significant circadian rhythm was documented for systolic and diastolic pressure, both under basal conditions and during placebo administration. Blood pressure mesors were higher than reference standards and were not significantly affected by placebo. The circadian amplitudes and acrophases did not differ significantly before and during placebo. Our data indicate that automatically recorded blood pressure is not influenced by placebo.

To estimate the possible involvement of a peripheral serotonergic pathway in the mechanism of the aldosterone-stimulating effect of metoclopramide (M) the plasma aldosterone (PA), renin activity (PRA)

The effects of pirenzepine (P), a cholinergic muscarinic antagonist, on growth hormone (GH) and prolactin (PRL) response to dermorphin (D) were studied in a group of 7 healthy men. D produced clear elevations in GH and PRL levels. P completely blocked the GH-releasing activity of D, whereas it did not alter the PRL-releasing activity. These results indicate that GH-releasing action of D is mediated via the central cholinergic nervous system in man.

The purpose of this study was to evaluate the effects of dermorphin, a new synthetic powerful opiate-like heptapeptide, on plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels in fertile and postmenopausal women. In fertile subjects, dermorphin (5.5 micrograms/kg min for 30 min) decreases plasma LH (p less than 0.01 vs. baseline and placebo values), but not plasma FSH. The area under the curve during dermorphin infusion was significantly lower than during placebo infusion (p less than 0.01). Pretreatment with the opioid receptor antagonist naloxone, blocked the decrease of plasma LH levels. In postmenopausal women not subjected to any treatment, dermorphin infusion did not significantly modify plasma LH and FSH levels. On the contrary, its administration to postmenopausal subjects treated with conjugated estrogens and medroxyprogesterone acetate significantly decreased plasma LH levels (p less than 0.01, vs. baseline, placebo and area under the curve). Considering the modulatory role exerted by ovarian steroids on the activity of such receptors, these data also indicate that opioid systems play a very important part in the hypothalamus-pituitary-ovarian axis.

We have recently shown that dermorphin (D), a new potent opioid peptide (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2) stimulates prolactin (PRL) and growth hormone (GH) secretion in humans. In 11 patients with a PRL-secreting pituitary adenoma (eight microprolactinomas and three macroprolactinomas with suprasellar extension), diagnosed by pituitary dynamic function tests, and radiological evidence with confirmation at surgery, the PRL and GH responses to D were studied to evaluate the effect of pathological hyperprolactinemia on the opioid-induced secretion of GH and PRL. No PRL response to D was observed in all 11 patients. Plasma GH increased after D in all patients, except in three patients bearing a macroprolactinoma. This study shows that the effect of D on PRL and GH secretion can be dissociated in patients with PRL-secreting pituitary adenoma, perhaps for a different derangement in the hypothalamic-pituitary mechanism(s) underlying the opioidergic regulation of GH and PRL secretion. In addition our data indicate that D can be employed as a useful opioid probe in humans.

The effect of intravenous administration (10 mg) of ketanserin , a pure, specific and selective blocking agent of 5-HT2 receptors (R 41 468: 3-{2-[4-(4-fluorobenzoyl)-1-pi

Five patients with severe hypothyroidism were studied to determine diurnal variations in serum TSH and thyroid hormones. The results were based on blood samples withdrawn at 1-h intervals during a 24-h period. A statistically significant circadian rhythm in TSH was detected with the acrophase at 23(30); no significant diurnal periodicity was observed for serum T3. The TSH pattern was similar to that observed in normal and midly hypothyroid subjects, with low levels during the day and higher levels at night. The findings are consistent with the following concepts: a. the TSH circadian rhythm is retained in patients with severe hypothyroidism; b. the abnormality in thyroid function does not effect the regulation of the TSH periodicity.

This study was designed to investigate the effect of dermorphin (D), a new synthetic potent opiate-like peptide (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), on PRA, plasma aldosterone (PA), plasma cortisol (PC), and plasma ACTH levels in normal men. D infusion (5.5 micrograms/kg X min for 30 min) significantly increased PRA (P less than 0.01) and decreased PC levels (P less than 0.02). D produced a small decrease in ACTH and a small increase in PA. Pretreatment with the opioid receptor antagonist naloxone (N) blunted the D-induced PRA increase and completely prevented the D-induced PC decrease, but enhanced PC and ACTH levels. These data indicate that the action of D is mediated through opioid receptors, and are consistent with the conclusion that 1) D, a new opioid peptide, increases PRA levels, perhaps via activation of the sympathetic nervous system, providing evidence that opioid peptides may exert an influence on renin secretion; and 2) D suppresses PC levels, perhaps by affecting ACTH secretion, corroborating previous observations that opioid peptides might affect the function of the pituitary-adrenocortical axis.

The aim of this study was to investigate further the influence of dermorphin (D), a new potent opioid peptide (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), on the functional activity of the pituitary-adrenocortical system in man. Six normal men were treated with oral metyrapone to stimulate the secretion of ACTH, beta-lipotropin, and beta-endorphin. In these subjects, significant suppression of metyrapone-evoked release of ACTH and related peptides occurred during D infusion (5.5 micrograms/kg X min for 30 min) compared with that during saline infusion. These results indicate that D can induce a significant decline in plasma levels of ACTH, beta-lipotropin, and beta-endorphin, the major circulating peptides from the C-terminal part of proopiocortin, and suggest that opioid peptides may be involved in the control of the functional activity of pituitary-adrenocortical activity in man.

Two new related heptapeptides (dermorphins) with potent central and peripheral opiate-like activity have been isolated from the skin of South American frogs, and have been chemically characterized as H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2 (dermorphin) and H-Tyr-D-Ala-Phe-Gly-Tyr-Hyp-Ser-NH2 (Hyp6-dermorphin). The response of GH to infusion of a synthetic dermorphin (5.5 micrograms/kg/min for 30 min) was studied in 9 healthy men. Dermorphin (D) significantly increased plasma growth hormone (GH) concentrations. The GH response to D was blunted by prior administration of naloxone, suggesting that D interacts with mu-type opiate receptors. However, the evaluation of the physiological significance of D-induced GH release in humans requires further study.

Dermorphin (D) is a potent opiate-like peptide isolated from the skin of some species of frogs. Experimental studies in animals indicate that D has a potent antinociceptive effect, while no investigation exists about its analgesic properties in humans. Our study shows that i.v. infusion of 0.16 mg/kg D induces a marked and long-lasting increase in the threshold of nociceptive flexion reflex in healthy volunteers. This effect is also evident in a complete chronic spinal subject, showing that D depresses the nociceptive transmission mainly acting at spinal level. Naloxone, while fully antagonizing the effects of morphine and enkephalin analogue, is able to reverse only partly (ca. 50%) the depressive effect of D on nociceptive spinal reflex. This fact may suggest that D interacts with different spinal opiate receptor populations in inducing analgesia.

This paper summarizes the results of our recent studies in a group of healthy subjects on the endocrine effects of the new potent opioid peptide, dermorphin (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), originally isolated from amphibian skin. Intravenous infusion (5.5 microgram/kg/min for 30 min) of dermorphin (D) significantly increased plasma levels of prolactin (PRL), growth hormone (GH), thyrotropin (TSH) and renin activity (PRA), but decreased plasma levels of cortisol. D produced a small decrease in ACTH, and a small increase in plasma aldosterone. Pretreatment with the opioid receptor antagonist naloxone (N) suppressed the PRL and TSH response to D, blunted the D-induced GH and PRA increase, and completely prevented the D-induced plasma cortisol decrease, but enhanced plasma cortisol and ACTH levels. These data indicate that the action of D is mediated through opioid receptors, and are consistent with the conclusion that: (1) D, a new opioid peptide, can stimulate PRL, GH and TSH release in humans; (2) D increases PRA levels, perhaps via activation of the sympathetic nervous system, providing evidence that opioid peptides may exert an influence on renin secretion; (3) D suppresses plasma cortisol levels, by affecting ACTH secretion, corroborating previous observations that opioid peptides might affect the function of the pituitary-adrenocortical axis.

In an attempt to examine the effect of prolonged physical activity on the function of the GH/IGF-1 axis during the aging process in man, we have evaluated basal and GHRH (GHRH-29: 1 microgram/kg i.v. as a bolus) stimulated GH secretion as well as basal plasma IGF-1 levels in a group of 25 healthy runners (50-60 years, mean age 55.5 +/- 0.6) and 24 age-matched relatively sedentary normal controls (mean age 55.8 +/- 0.7). The runners had a minimum distance in kilometers of 26 km/week for at least 15 years, and competed in distances ranging from 16 km to the marathon. In runners, GHRH induced an increase of GH which was significantly higher (p0.001) than that observed in the age-matched controls. Baseline IGF-1 levels were significantly higher (p0.001) in trained runners (171 +/- 8.4 micrograms/1) compared to the controls (91.1 +/- 5.5 micrograms/1). These data show that in middle-age prolonged physical activity increases the function of the GH/IGF-1 axis. To clarify the possible mechanisms underlying the GH/IGF-1 secretory pattern in the runners, the GH responses to both single and combined administration of GHRH and arginine (ARG: 30 g infused over 30 min), a GH secretagogue likely acting via inhibition of hypothalamic somatostatin release, were investigated in 6 runners (mean age 55 +/- 1.9 years) and 6 controls (mean age 55 +/- 0.9 years). ARG clearly increased the GH response to GHRH in the controls, whereas it was unable to further potentiate the GH-releasing effect of GHRH in runners, thus suggesting that the increased GH responsiveness to GHRH might be due to an exercise-related decrease in endogenous hypothalamic somatostatinergic activity.