Search

Objectives: Adrenocorticotrophin (ACTH) plays an important role in mediating the increase in cortisol output in the late gestation sheep fetus. At the adrenal itself, heightened expression of ACTH receptor (ACTH-R) and steroid acute regulatory protein (StAR) appear to be important parallel changes. This study examined how ACTH affects ACTH-R and StAR mRNA expression, and cortisol production in adrenocortical cells isolated from fetuses of varying gestational age (dGA). We hypothesized that the ability of ACTH to stimulate its receptor and StAR mRNA expression would be greater close to term than earlier in development., Methods: Adrenals were obtained from fetuses (100-105, 120, or 135-139 dGA), and the cortical cells were dispersed. After 3 days of culture, cells were stimulated with ACTH(1-24), and the cells and medium were collected at different time points (0, 3, 6, 9, 12, and 24 hours) for measurement of cortisol and ACTH-R and StAR mRNA., Results: Cortisol secretion was increased after ACTH treatment in all three age cohorts. Cells from the 135-139 dGA group secreted the most cortisol, followed by the 100-105 and then the 120 dGA groups (P <.05). ACTH-R mRNA levels before and after ACTH were higher in the late compared to both earlier groups. StAR mRNA levels before and after ACTH were higher in the 100-105 and 135 than in the 120 dGA group. The time to peak ACTH-R mRNA response was age-dependent, with the 100-105 dGA cells taking longer to attain maximum levels. Maximal StAR mRNA levels were not age-related., Conclusion: The data suggest that ACTH-R and StAR are indeed key mediators of fetal adrenocortical responsiveness, and that ACTH is able to up-regulate responsiveness, and hence cortisol production, by increasing their expression.

Although it is known that stresses on females damage oocytes with increased production of stress hormones, whether corticotrophin-releasing hormone (CRH) or adrenocorticotropic hormone (ACTH) harm oocytes directly are largely unknown. We demonstrated that CRH exposure during in vitro maturation impaired competence of both pig and mouse cumulus-oocyte-complexes (COCs), and it impaired competence and induced apoptosis in pig cumulus-denuded oocytes (DOs) but not in mouse DOs. CRH receptor 1 was expressed in pig DOs and in cumulus cells (CCs) of both species but not in mouse DOs. In the presence of CRH, whereas mouse CCs underwent apoptosis, pig CCs did not. While pig CCs did, mouse CCs did not express CRH-binding protein. ACTH did not affect competence of either pig or mouse COCs or DOs although they all expressed ACTH receptor. Both pig and mouse CCs expressed steroidogenic acute regulatory protein (StAR), and ACTH enhanced their progesterone production while alleviating their apoptosis. Neither pig nor mouse DOs expressed StAR, but ACTH inhibited maturation-promoting factor and decelerated meiotic progression of DOs suggesting activation of protein kinase A (PKA). In conclusion, CRH impaired pig and mouse oocyte competence by interacting with CRH receptor and inducing CCs apoptosis, respectively. ACTH activated PKA in both DOs and CCs although it showed no effect on oocyte competence., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Adrenocorticotropic hormone- (ACTH-)independent macronodular adrenal hyperplasia (AIMAH) is an infrequent cause of Cushing's syndrome (CS). AIMAH presents as incidental radiological finding or with subclinical or overt CS, occasionally with secretion of mineralocorticoids or sex steroids. The pathophysiology of this entity is heterogeneous. The aberrant adrenal expression and function of one or several G-protein-coupled receptors can lead to cell proliferation and abnormal regulation of steroidogenesis. In several familial cases of AIMAH, specific aberrant hormone receptors are functional in the adrenal of affected members. Additional somatic genetic events related to cell cycle regulation, adhesion and transcription factors occur in addition in the various nodules over time. Other mechanisms, such as Gsp or ACTH receptor mutations and paracrine adrenal hormonal secretion, have been rarely identified in other cases of AIMAH. The identification of aberrant receptors can offer a specific pharmacological approach to prevent progression and control abnormal steroidogenesis; alternatively, unilateral or bilateral adrenalectomy becomes the treatment of choice.

Inherited adrenocorticotropin (ACTH) resistance diseases are rare and include triple A syndrome and familial glucocorticoid deficiency (FGD). These conditions show genetic heterogeneity, i.e., the identical clinical phenotype may result from defects in more than one gene. Clinically, FGD is characterized only by ACTH resistance, while the triple A syndrome exhibits a variety of additional clinical features. FGD is caused by mutations in the ACTH receptor (melanocortin 2 receptor, MC2R) and the recently identified melanocortin 2 receptor accessory protein (MRAP) genes. In addition, linkage to a locus on chromosome 8 has been demonstrated. The identification of further genes in ACTH resistance syndromes may reveal novel aspects of MC2R signalling and trafficking. This review will summarize the clinical, biochemical and genetic aspects of these rare but informative diseases.

It is known that the stress hyporesponsive period (SHRP), which seems to be related to an immature hypothalamo-pituitary-adrenal (HPA) regulatory system, occurs during the first 2 weeks after birth in rats. In the present study, we investigated the effects of sex-steroid hormones on adrenocortical responsiveness to adrenocorticotropic hormone (ACTH) in neonatal rats. The levels of cyclic adenosine 3',5'-monophosphate (cAMP), corticosterone, and adenylate cyclase activity increased with the dose of ACTH in adrenal cells of males and females in vitro. The ACTH responsiveness in adrenal cells increased with age (7-35 days of age), that is, the loss in responsiveness to ACTH just after birth began to recover in 14-35-day-old rats, but the responsiveness in 14-day-old rats was attenuated in males compared with females. Although castration markedly augmented the responsiveness in male rats, testosterone-replacement in the castrated male rats inhibited the enhancement. Furthermore, the responsiveness in 14-day-intact female rats was suppressed by treatment with testosterone. Expression levels of ACTH receptor mRNA in adrenals increased with age in the female rat, but not in the male. Castration enhanced the level of ACTH receptor mRNA to three-fold of that in intact male rats at 14 days of age, but replacement treatment with testosterone in castrated male rats lowered the elevated levels. Testicular androgens are thought to evoke a gender-specific response in neonates, and the temporal decrease of adrenal ACTH-responsiveness might be due to the topically immature adrenal system as well as the central nervous system in mammals.

ACTH insensitivity results from a group of rare autosomal recessive genetic defects. Familial glucocorticoid deficiency is one of these syndromes in which about half of all cases have inactivating mutations of the ACTH receptor. The remaining patients with this syndrome have defects in one or more other as yet unidentified genes that are unlinked to the ACTH receptor. The triple A syndrome is a distinct clinical syndrome which includes alacrima (absence of tears), achalasia and various neurological defects in addition to ACTH insensitivity. In all cases the defect lies in a gene located on chromosome 12.

ACTH resistance syndromes consist of a group of rare disorders with three various molecular etiologies. However, all these diseases share the feature of severe glucocorticoid adrenal insufficiency. The simplest disorder is the isolated familial glucocorticoid deficiency (FGD) which could be divided in two different types. In FGD type 1, ACTH receptor mutations have been described and are responsible for the loss of function of the receptor, leading to the ACTH unresponsiveness. Patients with FGD type 2 show the same phenotype as in the previous syndrome but no mutation of the ACTH receptor has been reported in these cases. It has been proposed that morbidity of one or several other gene(s) could be responsible for this syndrome although there is no information about their chromosomal localization. The third molecular form of the disease corresponds to the Triple A syndrome for the triad of association "ACTH resistance, Achalasia, Alacrima", thus reflecting a large spectrum of additional symptoms. It has recently been reported that the morbid gene in this last syndrome maps to chromosome 12q13. The aim of this review is to examine the clinical aspect as well as the current knowledge of the molecular and genetic aspects of the different forms of the disease.

The effect of incubation temperature and ligand competition was tested for (125)I-ACTH binding to isolated rat lymphocytes. AlphaMSH but not Agouti-like peptide was an effective competitive inhibitor for cell surface binding at 4 degrees C. Cells incubated with (125)I-ACTH at 37 degrees C rapidly associated ligand for 10 min and then gradually lost the radioactivity with time. Cells incubated with (125)I-ACTH at 4 degrees C accumulated ligand to only about half the maximal amount when compared to cells incubated at 37 degrees C for 10 min. Temperatures below 20 degrees C and toxins that block lysosomal degradation blocked the loss of cell-associated radioactivity. These results suggest the lymphocyte ACTH receptor is the Melanocortin 5 receptor and the receptor is internalized by endocytosis to deliver ligand to the lysosome., (Copyright 1999 Academic Press.)

Chronic food restriction (FR) of rats and mice results in moderate hyperadrenocorticism, which may play a role in activating cellular mechanisms that retard aging. Previously, we reported that the FR-induced hyperadrenocorticism is not due to an activated hypothalamo-pituitary unit. Therefore, we investigated in a series of experiments whether adrenal responsiveness to adrenocorticotropic hormone (ACTH), in vitro and in vivo, is enhanced by FR. Three mo-old male Fischer 344 rats were either given free access to food (AL rats) or restricted to 60% of food consumed by AL rats (FR rats) from 6 wk of age. They were killed by decapitation in the morning (AM) and afternoon (PM) when endogenously circulating corticosterone levels are at their nadir and peak, respectively. In vitro, adrenal glands from FR rats (1.5 mo FR) produced more corticosterone per mg at all doses of ACTH than those from AL rats in both the AM and PM (diet main effect, P < 0.001). FR (1.5 to 2.5 mo) also enhanced adrenal responsiveness to physiologic (diet main effect, P < 0.05) and superphysiologic (diet main effect, P < 0.001) levels of ACTH administered in vivo to dexamethasone-treated rats. ACTH-receptor (ACTH-R) mRNA, normalized to adrenal mass or to total RNA, was not influenced by FR (1.5 mo). However, adrenal ACTH-R mRNA, as well as adrenal mass, per unit body weight was greater in FR than in AL rats (diet main effect, P < 0.001). These results indicate that enhanced adrenocortical responsiveness to ACTH plays a major role in the hyperadrenocortical state of chronically FR rats.

Using cultured bovine adrenal fasciculata cells (BAC), we investigated the effects of two hormones, corticotropin (ACTH) and angiotensin II (Ang-II) and two growth factors, insulin-like growth factors I (IGF-I) and transforming growth factor beta 1 (TGF beta 1), on the mRNA levels of nuclear proto-oncogenes of the Fos and Jun families and on the mRNA levels of genes expressed in BAC coding for ACTH and AT1 receptors, cytochrome P450scc and P450 17 alpha and 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). ACTH and IGF-1 increased c-fos and jun-B mRNA levels early with later increases in the levels of mRNA for the ACTH receptor and the three steroidogenic enzymes, and enhanced steroidogenic responses to both ACTH and Ang-II. In contrast, Ang-II increased mRNA coding for the three proto-oncogenes (cfos, c-jun, and jun-B), decreased those for P450 17 alpha and 3 beta-HSD, and caused marked homologous and heterologous steroidogenic desensitization. TGF beta 1 increased only jun-B mRNA and markedly reduced BAC-differentiated functions and steroidogenic responsiveness to both ACTH and Ang-II. The long-term effects of ACTH on human adrenal fasciculata cells were comparable with those observed in BAC, whereas the long term effects of Ang-II and TGF beta 1 were different from those observed in BAC. Whether these species-specific differences are related to a different effect of these factors on proto-oncogene expression is not yet known.

The molecular and species specificity of glucocorticoid suppression of corticosteroidogenesis was investigated in isolated adrenocortical cells. Trypsin-isolated cells from male rat, domestic fowl and bovine adrenal glands were incubated with or without steroidogenic agents and with or without steroids. Glucocorticoids were measured by radioimmunoassay or fluorometric assay after 1-2 h incubation. Glucocorticoids suppressed ACTH-induced steroidogenesis of isolated rat cells with the following relative potencies: corticosterone greater than cortisol = cortisone greater than dexamethasone. The mineralocorticoid, aldosterone did not affect steroidogenesis. Suppression by glucocorticoids was acute (within 1-2 h), and varied directly with the glucocorticoid concentration. Testosterone also suppressed ACTH-induced steroidogenesis. Glucocorticoid-type steroids have equivalent suppressive potencies, thus suggesting that these steroids may induce suppression at least partly by a common mechanism. Although corticosterone caused the greatest suppression, testosterone was more potent. The steroid specificity of suppression of cyclic AMP (cAMP)-induced and ACTH-induced steroidogenesis were similar, suggesting that suppression is not solely the result of interference with ACTH receptor function or the induction of adenylate cyclase activity. Exogenous glucocorticoids also suppressed ACTH-induced steroidogenesis of cells isolated from domestic fowl and beef adrenal glands, thus suggesting that this observed suppression may be a general mechanism of adrenocortical cell autoregulation.

Corticotropin (ACTH) has two main actions in mammalian adrenal cortex: acute stimulation of glucocorticoids secretion and trophic effect which allow the expression of genes encoding for the steroidogenic enzymes. The ACTH membrane bound receptor was one of the first to be demonstrated by direct binding of labeled hormone to subcellular preparations of the adrenal cortex. However, detection and characterization of physiological relevance to ACTH receptors has been difficult, because of the low biological activity of the labeled ACTH. Introduction of a bulky iodine atom into Tyr2 and the oxidation of Met4 appear to contribute most to the loss of activity. These difficulties were overcome recently by using an [125I]-ACTH labeled only in Tyr23, which retains full biological activity. Using this labeled hormone, physiologically relevant ACTH receptors, with high affinity (KD congruent to 10-10M) and low capacity (congruent to 2000 sites/cell) have been characterized in several mammals. A second site of low affinity (KD congruent to 10(-7M) and high capacity, has been found in some studies but the significance of this second site is unknown since it cannot be related to any physiological response of adrenal cells to ACTH. In contrast with the loss of receptors and desensitization of target cells caused by most polypeptide hormones, ACTH seems to regulate positively its own receptors and the cAMP response. The molecular weight of the ACTH receptor appears to be between 83 and 100 KD.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of naloxone on basal and ACTH, Angiotensin II (AII) and [K+] o stimulated aldosterone secretion from superfused rat adrenocortical tissue were investigated. A high dose (10(-6) M) of naloxone inhibited while a smaller dose (10(-10) M) potentiated and doses of 10(-8) or 10(-12) M naloxone were without an effect on ACTH stimulated aldosterone secretion. A potentiation of AII stimulated aldosterone secretion was observed beginning 2 hrs after 10(-6) or 10(-10) M naloxone was administered while no effect was observed with 10(-4) M naloxone. No effects of 10(-6), 10(-8), 10(-12) M naloxone were detected on aldosterone secretion stimulated by transiently elevating extracellular potassium. Naloxone from 10(-4) to 10(-12) M did not appear to significantly influence basal steroidogenic activity under these conditions. These findings demonstrate that the "opioid antagonist" naloxone has prominent actions on adrenocortical tissue. Both the specificity and lack of specificity of the action of this agent to influence the activity of the 3 secretagogues suggest that naloxone and possibly a naturally occurring endogenous ligand interacts with one or more membrane receptor distinct from the ACTH receptor. A naturally occurring ligand for this receptor could play a prominent role in the physiological regulation of adrenal steroid secretion.

Previous studies have suggested that suppression of fetal rabbit adrenocorticotropin (ACTH) secretion results in impaired development of ACTH-specific adenylate cyclase activity. In order to test this hypothesis we measured fetal and maternal plasma ACTH, cortisol, and corticosterone concentrations in control does and does infused with 0.3 mg of cortisol/hour at 21 to 24 days of gestation. This cortisol infusion regimen significantly depressed maternal and fetal plasma ACTH and corticosterone concentrations but did not change fetal serum cortisol concentrations. These findings further support the hypothesis that fetal ACTH plays a role in the normal development of the adenylate cyclase catalytic portion of the ACTH receptor complex and adrenal differentiation during this critical period of fetal life.