Search

We used antisense oligodeoxynucleotide (ODN) strategy, based on interference of information flow from gene to protein, to determine the role of kininogen and bradykinin B 2 receptor genes in the pathogenesis of genetic hypertension in rats. Mean blood pressure of 9-week-old spontaneously hypertensive rats (SHR) increased 4 hours after acute intracerebroventricular injection of synthetic 18-mer antisense ODNs targeting the translation initiation codon of kininogen mRNA (from 164±5 to 181±4 mm Hg, P 2 receptor mRNA (from 161±5 to 185±8 mm Hg, P 2 receptor mRNAs increased blood pressure of normotensive Wistar-Kyoto rats only slightly compared with SHR (from 116±3 to 124±1 and from 116±2 to 126±4 mm Hg, respectively; P 2 receptor mRNA. Microinjection of antisense ODN to B 2 receptor mRNA into the nucleus tractus solitarii increased mean blood pressure in SHR and prevented the vasodepressor effect induced by intranuclear microinjection of bradykinin. No significant change in mean blood pressure was induced in either strain by intravenous injection of antisense ODNs or by central injection of sense or scrambled ODNs. A strong fluorescent signal was detected at the level of the hippocampus, thalamus, hypothalamus periventricularis, midbrain, and cerebrum 1 hour after central injection of fluorescein isothiocyanate–conjugated antisense ODNs. Kininogen levels were significantly lower in the brain of rats given intracerebroventricular antisense kininogen ODN compared with controls. Our results indicate that the brain kallikrein-kinin system plays a role in the central regulation of blood pressure and suggest that this system may exert a protective action against further elevations of blood pressure levels in SHR.

Abstract To assess whether the cardiovascular effects induced by early blockade of bradykinin B 2 -receptors with Hoe 140 ( d -Arg[Hyp 3 ,Thi 5 , d -Tic 7 ,Oic 8 ]-bradykinin) are influenced by sex, Wistar rats of both sexes received the antagonist (300 nmol/d per kilogram body wt) or vehicle from 2 days to 7 weeks of age by subcutaneous injection and then by intraperitoneal infusion. Compared with control rats, Hoe 140–treated female rats showed higher systolic blood pressure levels at 7 and 9 weeks of age (125±2 versus 111±2 mm Hg and 132±3 versus 116±2 mm Hg, respectively, P P P P P P

Adrenomedullin (ADM) infusion increases salt excretion in the rat. However, there is no evidence that this substance is related to changes in salt intake in humans. In this study we sought whether the urinary excretion rate of this autacoid is related to salt intake and by the expected changes in arterial pressure in patients with mild essential hypertension. The influence of salt intake on the renal excretion of ADM was investigated in 55 hypertensive patients in a double blind, randomized and crossover study comparing a 2-week 50 mmol/day salt intake period with a 150 mmol/day salt intake period. Twenty-four-hour ADM and endothelin-1 (ET-1) excretion rate were measured by radioimmunoassay on preextracted urinary samples (intraassay confidence variable

Identifying the genetic predictors of the therapeutic response to drugs is the role of pharmacogenomics. Although polymorphisms in several genes have been associated with the blood pressure response to diuretics, beta-blockers and ACE-inhibitors, the pharmacogenomics of essential hypertension is still attempting to find satisfactory scientific evidence to be translated into clinical practice. The main reasons for this apparent failure are: the small sample sizes of the cohorts of patients analyzed, the methodological variability, the complexity of the biological organization, the context-dependency and the genetic heterogeneity. This review will summarize the available data on antihypertensive drugs and the criteria used for study design and conduction, focusing on their strong points and limitations.

We investigated the influence of salt intake on urinary and plasma endothelin-1 (ET-1) in 55 patients who entered a two-week double-blind, randomised, crossover study comparing a 50 mMol/day salt intake and 150 mMol/day. Twenty-four-hour ET-1 excretion and plasma ET-1 were measured by RIA on pre-extracted samples.In the whole cohort (n=55), changes in urinary ET-1 were related to salt excretion (r=0.28, P=0.04) and urinary volume (r=0.47, P=0.0001). In a multivariable model, changes in PRA, plasma aldosterone, blood pressure and heart rate did not add any predictive power to salt excretion with regard to urinary ET-1 variations. The relationship between urinary volume and urinary ET-1 was stronger than that of urinary sodium with ET-1 excretion because sodium was excluded from the multivariable model when urinary volume was introduced. Changes in urinary ET-1 were unrelated to mean blood pressure changes (P=0.66). Changes in plasma ET-1 were unaffected by changes in salt intake (P=0.58) but were strongly related to those in PRA (r= -0.45, P=0.01) and plasma aldosterone (r= -0.53, P=0.002).The renal excretion of ET-1 is influenced by changes in salt intake and appears largely independent of the blood pressure response to salt. Changes in urinary volume which accompany variations in salt excretion play an important role in this response. Since urinary ET-1 reflects its renal synthesis, our data support the notion that renal ET-1 plays a role in the regulation of sodium balance in patients with mild hypertension.

1. Tissue kallikrein is overexpressed in the kidney of female rats, this sexual dimorphism being associated with a greater effect of early blockade of bradykinin B2-receptors on female blood pressure phenotype. We evaluated the effect of ovariectomy and oestradiol benzoate (50 micrograms kg-1 every two days for two weeks) on the vasodepressor response to intra-arterial injection of bradykinin (150-900 ng kg-1) and on the expression of bradykinin B2-receptors. 2. Ovariectomy reduced the magnitude of the vasodepressor response to bradykinin and unmasked a secondary vasopressor effect. Oestrogen replacement restored the vasodepressor response to bradykinin in ovariectomized rats. 3. The vasodepressor responses to sodium nitroprusside (3-18 micrograms kg-1), acetylcholine (30-600 ng kg-1), desArg9-bradykinin (150-900 ng kg-1) or prostaglandin E2 (30-600 ng kg-1) were significantly reduced by ovariectomy. Oestrogen restored to normal the responses to desArg9-bradykinin, acetylcholine and prostaglandin E2, but not that to sodium nitroprusside. 4. B2-receptor mRNA levels were decreased by ovariectomy in the aorta and kidney and they were restored to normal levels by oestrogen. Neither ovariectomy nor oestradiol affected receptor expression in the heart and uterus. 5. These results indicate that oestrogen regulates B2-receptor gene expression and function. Since kinins exert a cardiovascular protective action, reduction in their vasodilator activity after menopause might contribute to the increased risk of pathological cardiovascular events. Conversely, the cardioprotective effects of oestrogen replacement might be, at least in part, mediated by activation of the kallikrein-kinin system.

In a large group of patients with untreated hypertension, excretion rates of tetrahydrocorticosterone (THB), allotetrahydrocorticosterone (alloTHB) and tetrahydro-11-dehydrocorticosterone (THA) were all significantly higher than in a group of matched normotensive controls. Using the sum of these metabolites as an index of corticosterone secretion rate suggests that this variable is also higher. The increase was small (all excretion rates remained within the normal range) and corticosterone has low glucocorticoid and mineralocorticoid potency calling the clinical significance of this finding into question. However, it is possible that in combination with mildly deficient 11 beta-hydroxysteroid dehydrogenase activity such increases in corticosterone levels might affect blood pressure.

1. The contribution of endogenous kinins to the regulation of blood pressure of angiotensin-treated rats was evaluated using the new bradykinin B2-receptor antagonist Hoe 140 (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin). 2. Chronic intraperitoneal infusion of 20 nmol/day angiotensin II did not alter systolic blood pressure or plasma angiotensin II levels. A significant increase in plasma aldosterone and corticosterone levels was observed after 4 weeks (from 89 +/- 20 to 140 +/- 22 and from 147 +/- 30 to 225 +/- 33 pg/ml, respectively; P0.05). 3. Combined administration of 20 nmol/day angiotensin II and 75 nmol Hoe 140 induced a significant increase in systolic blood pressure from 126 +/- 3 to 142 +/- 3 and 137 +/- 3 mmHg, at 1 and 4 weeks, respectively (P0.05). This effect was not accompanied by significant changes in plasma angiotensin II concentration. The angiotensin-induced increase in plasma levels of aldosterone and corticosterone was not altered by the antagonist Hoe 140. 4. These findings indicate that blockade of endogenous kinin receptors enhances the slow pressor effect induced by angiotensin II. Therefore, endogenous kinins may play a role in preventing the cardiovascular effects of an excess of vasoconstrictors.

We compared the response of blood pressure (BP) to either K-Canrenoate (K-Can) or hydrochlorothiazide (HCTZ) in 26 mild-to-moderate essential hypertensives in a double-blind, cross-over design over 2 months each. The dose was 12.5 mg o.d. for HCTZ and 50 mg o.d. for K-Can: dosing was doubled after 1 month if seated diastolic BP wasor = 95 mmHg. Eight pts were "selective responder" to the lowest dose of HCTZ (HCTZ-R), and 6 to K-Can (K-Can-R). Seven pts had their high blood pressure controlled by the highest dose of both drugs and 4 were insensitive to both. One pt dropped out during HCTZ for low plasma K+, and 3 during K-Can (nausea and dizziness: 2 pts; plasma creatinine rise: 1 pt). All these side effects were reverted after drug withdrawal. HCTZ-R and K-Can-R differed for PRA (1.4 +/- 0.6 vs 0.8 +/- 0.4 Ang I ng/ml/h, p0.05) and Na-K-Cl cotransport (230 +/- 39 vs 372 +/- 24 mumolNa/L RBC/h, p0.01). Our data suggest the existence of a subgroup of essential hypertensives surprisingly insensitive to HCTZ, characterized by a "low" PRA and by a Na(+)-K(+)-Cl- cotransport higher than the HCTZ-R. Their selective response to K-Can suggest a peculiar pathogenetic mechanism underlying their high blood pressure.

Furosemide at a dose of 3 mg/kg body wt increased urinary volume (vehicle: 12.8 +/- 0.6; furosemide: 42.4 +/- 2.6 ml/8h, p0.01) and urinary sodium excretion (vehicle: 0.9 +/- 0.1; furosemide: 5.0 +/- 0.4 mM/8h, p0.01) in deoxycorticosterone-treated rats. These effects were associated to a decrease in mean blood pressure (from 122 +/- 4 to 113 +/- 3 mmHg, p0.01) and renal vascular resistances (from 15.6 +/- 0.6 to 14.3 +/- 0.7 RU, p0.05). The B2-receptor antagonist D-Arg[Hyp3,Thi5,D-Tic7,Oic8]-bradykinin significantly blunted the diuretic and natriuretic effect of furosemide and completely prevented the decrease in blood pressure and renal vascular resistances. The renal kallikrein-kinin system may modulate the diuretic and hemodynamic effects of furosemide in conditions of increased mineralcorticoid activity.

We evaluated the effects of the B2-receptor antagonist Ac-D-Arg[Hyp3,D-Phe7,Leu8]-bradykinin on mean blood pressure (MBP) and Doppler mesenteric blood flow (DMBF). The antagonist, at a dose able to completely block the hemodynamic effects of exogenous bradykinin, increased MBP by 3 +/- 1% and decreased DMBF by 12 +/- 3%. These responses persisted after pharmacological neuro-hormonal blockade. Our results suggest that the kallikrein-kinin system plays a role in the regulation of mesenteric blood flow in rats.

Activation of semipurified human kidney prorenin was found to occur in vitro in presence of a mixture of lipids that mimics the composition of the inner human cell membrane. The lipid-dependent activation was indeed only partial (38 +/- 4%) when compared to that obtained by trypsin in liquid phase (100 micrograms/mL) used as a control of maximal activation (100%) under our experimental conditions (semipurified human kidney prorenin in presence of semipurified human plasma renin substrate at a concentration of 1400 ng/mL, at pH 7.2). The phenomenon was time-dependent up to 60 min whereas the angiotensin I generated after 120 min was virtually the same as that generated after 60 min thus indicating a possible reversible activation of human prorenin. We speculate that prorenin may be reversibly activated by contact with the lipidic portion of the cell membrane either inside or outside the cells thus allowing a limited angiotensin II-generating cascade at a local site initiated by prorenin independently from the presence of active renin.

The effects and clearance of synthetic atrial natriuretic peptide (alpha-hANP) were investigated in eight patients with end-stage renal failure and six normal volunteers. ANP or vehicle was infused for 1 h at 10 pmol.kg-1.min-1 in random order on two separate occasions. During ANP infusions in end-stage renal patients, microhematocrit rose by 9.8 +/- 2% (P less than 0.005, n = 8), from base-line values of 0.24 +/- 0.02. Serum protein and albumin rose consistently. In contrast, during placebo infusions, no significant changes were seen. Blood pressure, heart rate, plasma renin concentration, serum creatinine, and electrolytes did not change significantly during either study phase. In end-stage renal failure patients, metabolic clearance rate of infused ANP was 1.04 +/- 0.095 l/min and its plasma half-life was 4 min 34 s. In normal volunteers, metabolic clearance rate was 2.6 l/min and its plasma half-life 3 min 30 s. The data suggest that ANP promotes contraction of plasma volume via a mechanism independent of renal function and also indicate that the kidney is not the only organ involved in the ANP metabolism.

Purpose of this study has been to compare the results obtained using two different procedures in blood sampling from the renal veins for measuring renal venous renin. The first is the classical procedure which employs three catheters for simultaneous sampling from both renal veins and from the inferior vena cava, or from an artery. The other one is a simplified procedure which employs a single catheter that allows blood to be collected in the following rapid sequential manner: right renal vein, inferior vena cava, left renal vein, inferior vena cava. We have studied 13 patients (8 with essential hypertension, 5 with unilateral renal artery stenosis). Two catheters were introduced through a femoral vein and inserted into both renal veins; a third catheter was inserted into the femoral artery; then the blood sampling was performed strictly simultaneously. Soon after, the blood sampling was repeated according to the above mentioned sequential single catheter procedure. PRA was measured by Angiotensin I radioimmunoassay, then the Renal Vein Ratios (RVRR) were calculated. Even though as average of less than 20 seconds elapsed between the blood sampling in a renal vein and that in inferior vena cava, our results demonstrate that the release of renin can vary so quickly that erroneous informations may be obtained unless a strictly simultaneous sampling of blood is performed. In conclusion, our study demonstrates that the only reliable renal vein renin sampling procedure must employ the simultaneous renal venous and arterial (or inferior vena cava) blood collection.

The effects of aprotinin on renin release and renal function were evaluated in 24 male essential hypertensive patients, on unrestricted (N = 17) and on chronic low as well as on high Na intake. Aprotinin (1 x 10(6) KIU) or Saline (200 ml) were infused in all patients for 6 hrs. Blood samples were taken for plasma renin activity (PRA) and 6-hr urine collections were obtained for active and inactive kallikrein, Na+, K+, Cl-, Ca++ excretion measurements. In patients on unrestricted sodium diet aprotinin had no effect on BP, glomerular filtration rate, renal plasma flow, urinary sodium and potassium excretion. However an inverse relationship was found between pretreatment urinary sodium excretion and the percent reduction of the latter after aprotinin. A significant reduction in urinary sodium excretion was induced by aprotinin in patients on high sodium intake, whereas no change was observed in the same patients when on low sodium diet. Aprotinin reduced the urinary excretion of active kallikrein by 81% and the active to total kallikrein ratio from 24% to 6%, suggesting that it could interfere with the in-vivo activation of inactive kallikrein. Infusion of aprotinin induced a significant decline in active renin but did not modify inactive renin levels in patients on unrestricted sodium diet as well as in patients on low or high sodium intake. Our data suggest that the inhibition of kallikrein and/or other serine proteases by aprotinin can interfere with renal release of active renin and also support the hypothesis that the renal kallikrein system exerts a regulatory control on sodium excretion in salt replete hypertensives.

High tissue levels of angiotensin II have been reported in the median eminence suggesting a possible role in the regulation of adrenocorticotrophic hormone (ACTH) secretion. To verify this hypothesis in man, the pituitary-adrenal axis response to hypoglycaemia was studied before and during captopril treatment in eight male essential hypertensive patients (stage I WHO; aged 35-52 years). Plasma levels of ACTH, cortisol and glucose were measured before and 60, 90 and 120 min after an intravenous bolus of normal saline as placebo an, 3 days later, after an intravenous bolus of rapidly acting insulin (0.1 IU/kg body weight). Captopril treatment was then started and both placebo and hypoglycaemic tests were repeated 15 days thereafter. No changes in ACTH, cortisol or glucose plasma levels were observed after acute normal saline, either before or during captopril administration. On the contrary, hypoglycaemia induced a sharp increase of ACTH plasma before captopril (from 27.7 +/- 11 to 131.30 +/- 26 pg/ml, P less than 0.01, 60 min after insulin) but not during angiotensin converting enzyme (ACE) inhibition (from 28.9 +/- 9 to 42.9 +/- 11 pg/ml, NS, at min 60 of the study). Our present data, showing a blunted ACTH response to hypoglycaemia during ACE inhibition, suggest that circulating angiotensin II may participate in the regulation of the release of the ACTH, possibly by a stimulation of angiotensin II receptors localized in the brain but outside the blood-brain barrier.

Red cell membrane Na(+)-K+ transport systems, renin-angiotensin-aldosterone system (RAAS) and atrial natriuretic factor (ANF) were studied in a group of 50 mild essential hypertensive patients (n = 25 for each group) age, sex and blood pressure matched. Na(+)-K+ ATPase and intracellular Na+ (Na+ i) were significantly different between the two groups (p less than 0.01). A slight difference was also seen for the Na(+)-K+ cotransport (p less than 0.05) as a likely consequence of the differences in the methodology of Na+ charge to study its efflux from the red cells in vitro. A negative correlation (r = -0.47, p less than 0.01) was observed between ANF and Na(+)-K+ cotransport suggesting an interrelationship of the two systems in the homeostasis in body fluid and electrolytes.

Activation of semipurified human kidney prorenin was found to occur in vitro in presence of a mixture of lipids that mimics the composition of the inner human cell membrane. The lipid-dependent activation was indeed only partial (38 +/- 4%) when compared to that obtained by trypsin in liquid phase (100 micrograms/mL) used as a control of maximal activation (100%) under our experimental conditions (semipurified human kidney prorenin in presence of semipurified human plasma renin substrate at a concentration of 1400 ng/mL, at pH 7.2). The phenomenon was time-dependent up to 60 min whereas the angiotensin I generated after 120 min was virtually the same as that generated after 60 min thus indicating a possible reversible activation of human prorenin. We speculate that prorenin may be reversibly activated by contact with the lipidic portion of the cell membrane either inside or outside the cells thus allowing a limited angiotensin II-generating cascade at a local site initiated by prorenin independently from the presence of active renin.

We describe a case of a 26-year old woman with severe fibromuscular renal artery stenosis whose blood pressure was well controlled with atenolol but that remained normotensive also after discontinuation of the drug. In addition her renal vein renin pattern was typical of renovascular hypertension and an intrarenal activation of inactive renin was also present. This renin pattern remained unchanged soon after successful percutaneous transluminal dilatation whereas 15 days later both active and inactive forms of renin were found to be released by the previously stenotic kidney. This case casts doubts upon the relationships between renal artery stenosis, renin secretion and high blood pressure.

To explore the time-course and the source of the changes in plasma prorenin that occur in early pregnancy we studied a normal subject (subject 1), an in vitro fertilization (IVF) patient (subject 2) and an ovarian failure patient who received a donor egg (subject 3). Day 0 was the luteinizing hormone (LH) peak (subject 1), the day of human chorionic gonadotropin (hCG) administration (subject 2) or 3 days before embryo transfer (subject 3). In subjects 1 and 2 prorenin increased transiently (three- and ninefold respectively) on days 0-4, then returned towards baseline and began to increase again around day 12 to a maximum (six- and 26-fold baseline) around day 20. Active renin was consistently less than 10% of total renin. In the ovarian-failure patient only small fluctuations occurred in total renin yet her hCG was 137 mlU/ml on day 15, proving that she was pregnant. These results suggest that the prorenin rise that occurs at mid-menstrual cycle and following conception may be due to ovarian prorenin secretion in response to stimulation by gonadotropic hormones.

Semipurified human kidney prorenin was exposed in vitro to a mixture of lipids mimicking the composition of the inner leaflet of the cell membrane, in the presence of semipurified human angiotensinogen at a concentration of 1/4 Km. Prorenin was activated in a time-dependent manner over a period of 60 min. This lipid-dependent activation was completely reversed thereafter. Pre-incubation with anti-renin serum completely prevented this activated prorenin-dependent generation of angiotensin I. Our data suggest that human prorenin can be reversibly activated by contact with the cell membrane.

We have observed a significant higher prevalence of essential hypertension, cardiovascular diseases and diabetes in a group of 100 psoriatic patients compared with sex and age matched hospitalized controls. Thirty-five psoriatic patients exhibited and enhanced plasma renin activity (PRA), while urinary aldosterone excretion was raised in 27% of the group. The autonomic responsiveness of psoriatic patients, studied by cold pressure test and tilting was normal; this finding supports the hypothesis that the enhanced activity of renin-angiotensin system is not due to an increased sympathetic function in these psoriatic patients. High values of cholesterol, triglycerides and depressed HDL-cholesterol concentrations were also observed. A complete clinical and laboratory examination is very useful in psoriasis in order to initiate an appropriate treatment of the risk factors whenever present.

This multicenter trial in essential hypertensive patients (n=94) is aimed i) to evaluate the distribution of blood pressure salt-sensitivity by a rapid volume expansion/contraction protocol over three days; ii) to investigate the within-patient reproducibility and to identify predictors of the response to the test; iii) to compare this response with the response to dietary NaCl restriction.The study design included: 1) screening for salt-sensitivity by the rapid test; 2) a controlled trial of dietary salt restriction; 3) repetition of the rapid test in a subgroup of patients.The mean BP response to the rapid test fitted a Gaussian curve. In multivariate regression analysis, controlling for the effect of potential confounders, the blood pressure increment during the intravenous saline infusion was the best independent predictor of the response to the test (r=0.713) with minor contributions by the 24-h urinary sodium excretion before the test and by baseline fasting serum insulin. These three variables together explained 61\% of the overall variability of the response. The Spearman rank correlation coefficient between the BP response to the rapid test and the response to the dietary protocol was 0.21, p=0.05. Upon repetition of the rapid test, the correlation coefficient between the responses observed on the two occasions was 0.60 (n=19, p

OBJECTIVE: The aim of this study was to evaluate the effect of trandolapril, an angiotensin converting enzyme inhibitor, on blood pressure, forearm blood flow and insulin sensitivity in comparison with nifedipine gastrointestinal therapeutic system. PATIENTS AND METHODS: This is a multicentre, two-way parallel-group, open-label comparative study in 90 overweight hypertensive patients, who were randomly assigned to treatment for 8 weeks with either trandolapril or nifedipine. At baseline and after treatment, all patients underwent an oral glucose tolerance test, an evaluation of their metabolic profiles and a euglycaemic hyperinsulinaemic clamp test. In a subgroup of 18 patients, a forearm study was carried out. RESULTS: Blood pressure fell by the second week of treatment and remained significantly reduced compared with baseline in both treatment groups. Plasma triglyceride levels were also significantly reduced after trandolapril therapy, but no significant changes occurred in the other metabolic parameters during treatment with either drug. During the euglycaemic hyperinsulinaemic clamp, whole-body glucose use was similar in the two treatment groups at baseline, and a moderate but statistically significant increase in insulin sensitivity was observed after trandolapril treatment (trandolapril: 5.0 +/- 0.2 versus 4.5 +/- 0.2 mg/kg per min; nifedipine: 4.1 +/- 0.3 versus 4.2 +/- 0.3 mg/kg per min; P < 0.05, versus baseline and trandolapril versus nifedipine treatment). Skeletal muscle glucose uptake was significantly higher after trandolapril than after nifedipine therapy (5.0 +/- 0.7 and 3.0 +/- 0.4 mg/min, respectively; P < 0.01). As forearm blood flow was similar in the two treatment groups at baseline and was unchanged after 8 weeks of therapy, skeletal muscle glucose extraction was significantly greater in the ACE inhibitor treated-group than in the nifedipine comparative group (trandolapril: baseline 21 +/- 2, treatment 24 +/- 3 mg/dl; nifedipine: baseline 18 +/- 3, treatment 16 +/- 2 mg/dl; P < 0.05, trandolapril versus nifedipine treatment). CONCLUSIONS: During short-term treatment, ACE inhibition with trandolapril was able to moderately improve insulin sensitivity, in comparison with calcium blockade, and this effect appeared to be independent of the haemodynamic action of the drug.