Previous studies, by this group and others, have shown that vasoactive intestinal peptide (VIP) stimulates aldosterone secretion, and that the actions of VIP on aldosterone secretion by the rat adrenal cortex are blocked by beta adrenergic antagonists, suggesting that VIP may act by the local release of catecholamines. The present studies were designed to test this hypothesis further, by measuring catecholamine release by adrenal capsular tissue in response to VIP stimulation. Using intact capsular tissue it was found that VIP caused a dose-dependent increase in aldosterone secretion, with a concomitant increase in both adrenaline and noradrenaline release. The effects of VIP on aldosterone secretion were inhibited by atenolol, a beta1 adrenergic antagonist, but not by ICI-118,551, a beta2 adrenergic antagonist. Binding studies were carried out to investigate VIP receptors. It was found that adrenal zona glomerulosa tissue from control rats contained specific VIP binding sites (Bmax 853+/-101 fmol/mg protein; Kd 2.26+/-0.45 nmol/l). VIP binding was not displaced by ACTH, angiotensin II or by either of the beta adrenergic antagonists. The response to VIP in adrenals obtained from rats fed a low sodium diet was also investigated. Previous studies have found that adrenals from animals on a low sodium diet exhibit increased responsiveness to VIP. Specific VIP binding sites were identified, although the concentration or affinity of binding sites in the low sodium group was not significantly different from the controls. In the low sodium group VIP was found to increase catecholamine release to the same extent as in the control group, however, in contrast to the control group, the adrenal response to VIP was not altered by adrenergic antagonists in the low sodium group. These data provide strong support for the hypothesis that VIP acts by the local release of catecholamines in adrenal zona glomerulosa tissue in normal animals. It does not appear that VIP acts through the same mechanism in animals maintained on a low sodium diet. The mechanism by which VIP stimulates aldosterone in this group remains to be determined.
JP Hinson, Puddefoot JR, and S Kapas
J. M. C. Connell, C. J. Kenyon, S. G. Ball, D. L. Davies, and R. Fraser
The effect of dopamine (1 μg/kg per min) on corticosteroid response to ACTH (0·1, 1 and 10 ng/kg per min) was compared with that of a placebo in sodium-replete (150 mmol/day) and -deplete (10 mmol/day) normal man. Dopamine had no effect on aldosterone, cortisol or corticosterone responses in either dietary phase, but increased deoxycorticosterone (897·0 ± 126·4 (s.e.m.) vs 590·0 ±84·3 pmol/l, normal Na+; 1264·2 ±84·3 vs 764·5 ±84·3 pmol/l, low Na+) and deoxycortisol (6·033 ± 0·583 vs 5·048±0·680 nmol/l, normal Na+; 5·112 ± 0·600 vs 4·130± 0·367 nmol/l, low Na+) levels during ACTH administration (all P <0·01). Deoxycorticosterone and corticosterone responses to ACTH were greater during sodium depletion than repletion (both P <0·01).
Dopamine therefore increased 11-deoxycorticosteroid concentrations during ACTH-stimulated steroidogenesis. This may reflect action of dopamine to increase extra-adrenal formation of 11-deoxycorticosteroids.
J. Endocr. (1986) 109, 339–344
T. W. DOOUSS, S. J. M. SKINNER, and R. A. F. COUCH
The role of pregnenolone sulphate in adrenal steroid biosynthesis and the ability of the human adrenal gland to synthesize and secrete dehydroepiandrosterone (DHA) and dehydroepiandrosterone sulphate (DHA sulphate) was investigated. The presence of pregnenolone sulphate and DHA sulphate was demonstrated by measuring their concentrations in human adrenal tissue. Pregnenolone sulphate was metabolized in vitro mainly to free steroids, including DHA and cortisol, as well as directly to DHA sulphate in some cases. Similar results were obtained upon perfusion of the adrenal gland in situ with [14C]pregnenolone and [3H]pregnenolone sulphate as the substrates and isolating the metabolites from the adrenal venous blood. Dehydroepiandrosterone sulphate was derived mainly from the sulphation of free DHA. The hydrolysis of DHA sulphate did not appear to make a significant contribution to the amounts of DHA synthesized under these conditions.
The adrenal secretion of DHA and DHA sulphate by eight patients undergoing adrenalectomy was determined by measuring the concentrations of these compounds in samples of adrenal and peripheral venous blood taken simultaneously. In one patient secretion of DHA and DHA sulphate was equivalent whilst in the remainder there was much greater secretion of DHA.
P. W. NATHANIELSZ and MARGARET ABEL
Glucocorticoids secreted by the foetal adrenal cortex play a major causative role in initiating parturition in the sheep and goat (Liggins, 1968, 1969a; Bassett & Thorburn, 1969; Comline, Nathanielsz, Paisey & Silver, 1970; Thorburn, Nicol, Bassett, Shutt & Cox, 1972). However, Liggins (1969b) failed to precipitate premature parturition with dexamethasone (4 mg/h) infused into the maternal circulation of the pregnant ewe. Fylling (1971) produced delivery with 6–10 mg dexamethasone/day in the pregnant ewe. Since it is uncertain what role glucocorticoids may play in polytocous species, an attempt was made to initiate parturition by infusing cortisol into the maternal circulation of the pregnant rabbit. Cortisol was chosen as the glucocorticoid for infusion since in the newborn rabbit the plasma cortisol: corticosterone ratio is about 3·0 (K. W. Malinowska, R. N. Hardy & P. W. Nathanielsz, unpublished observations).
Pregnant rabbits of known gestational age were anaesthetized with sodium pentobarbitone (30–45
K. KOVÁCS, MARGIT A. DÁVID, and F. A. LÁSZLÓ
Lesions were made in the pituitary stalk of rats, and the functional capacity of the hypophysial-adrenocortical axis of animals suffering from diabetes insipidus was studied. Eight days after the operation the weight, histological structure and histologically demonstrated lipid content of the adrenals had not changed. Whereas operative stress and unilateral adrenalectomy caused no ascorbic acid depletion in the contralateral adrenals, administration of adrenocorticotrophic hormone induced a significant decrease. The corticosterone content of the adrenal venous blood decreased moderately, whilst in vitro the adrenal slices secreted less corticosterone than normally. Secretion of aldosterone by the adrenals of animals with lesions was not different from that of controls. When large doses of corticosterone were administered adrenal atrophy occurred in both operated and control rats.
It is concluded that the functional capacity of the hypophysial—adrenocortical axis is decreased 8 days after the destruction of the pituitary stalk, although the production of hormones by the adrenal cortex does not cease completely; one must be cautious in assessing the functional state of the adrenal glands since the methods used for their evaluation do not always give comparable results.
M Fraser, GA Braems, and Challis JR
Responsiveness of the fetal sheep adrenal gland to adrenocorticotrophin (ACTH) increases in late pregnancy, resulting in increased glucocorticoid production. Development of this responsiveness is an important determinant of fetal hypothalamic-pituitary-adrenal function and depends, in part, on the potential for ACTH binding to adrenal tissue. In the present study, we have examined the developmental pattern of ACTH receptor (ACTH-R) expression during the latter half of pregnancy and in neonatal and adult life. As hypoxaemia induces increases in cortisol and ACTH secretion, in addition to increasing fetal adrenal responsiveness, a further aim of this study was to investigate whether hypoxaemia was associated with altered expression of the ACTH-R gene. Whole adrenal glands were removed from fetal sheep, lambs and adult sheep at different stages of development for measurement of ACTH-R mRNA. Moderate hypoxaemia was induced for 48 h beginning on days 124-128, or on days 132-134 of gestation, by decreasing the maternal fractional inspired oxygen. ACTH-R mRNA was detected by northern blotting using a cDNA cloned in our laboratory and by in situ hybridisation. ACTH-R mRNA (3.6 kb major transcript) was detected in adrenal tissue at day 63 of gestation. Its relative abundance increased significantly (P<0.05) between days 126-128 and 140-141 of pregnancy, increased further with the onset of spontaneous labour, and remained increased in newborn lambs at 7 h-7 days after birth. ACTH-R mRNA levels then decreased in adrenal tissue from lambs and adult sheep (P<0.05). Hypoxaemia for 48 h significantly increased ACTH-R mRNA expression in adrenals of the older fetuses (days 134-136) compared with that in controls (P<0.05), but was without effect in younger fetuses. We conclude that levels of ACTH-R mRNA in the fetal adrenal gland increase as term approaches, coincident with the endogenous prepartum surge in plasma ACTH and cortisol. Sustained hypoxaemia resulted in an upregulation of mRNA encoding for ACTH-R, but only in older fetuses and in association with a sustained increase in plasma cortisol. These results are consistent with cortisol, ACTH, or both, contributing to increased fetal adrenal responsiveness, by increasing expression of fetal adrenal receptors for ACTH.
I. CHESTER JONES, G. P. VINSON, I. G. JARRETT, and G. B. SHARMAN
Mature female brush-tailed possum (Trichosurus vulpecula Kerr) were captured locally and kept in the grounds of the Department of Zoology, University of Adelaide. Animals were anaesthetized by sodium pentobarbitone (Abbott). Glucosesaline (5% glucose in 0·9% NaCl solution) was given i.v. as required. The left adrenal gland was exposed and cannulated by a modification of the method of Bush & Ferguson (1953) for sheep. Subsidiary vessels were tied off and the adrenal venous blood led into a measuring cylinder kept in packed ice. The blood was centrifuged and kept deep-frozen for analysis.
The plasma was extracted according to the method of Bondy, Abelson, Scheuer, Tseu & Upton (1957). Extracts were developed chromatographically, initially in the system L/75 (Bush, 1952, 1961). The origins of these chromatograms were eluted and re-run in system T/70 (Bush, 1961). One compound was considered to be cortisol on the following grounds: (i) the compound had an RF
M Dodic, M Tersteeg, A Jefferies, EM Wintour, and K Moritz
Low-dose dexamethasone treatment is used in pregnancies where the fetus is suspected to be at risk of congenital adrenal hyperplasia (CAH). In order to see if such treatment had long-term effects, pregnant ewes were treated with dexamethasone (20 micro g/kg maternal body weight) or saline from 25 to 45 days of gestation and blood pressure and renal function studied in offspring at 2 Years of age. There were 11 animals from dexamethasone treatment (six females and five males) and nine lambs from saline treatment (five females and four males). We aimed to study blood pressure and heart rate in the adult animals of both genders, and renal function only in the adult female animals.In both females and males, blood pressure and heart rate were similar between the two groups of animals. The excretion rates of sodium and potassium were similar between the two groups of animals. In addition, glomerular filtration rate was not different between the two groups of animals (112+/-11 ml/kg per h (S.E.M.) in saline-treated females vs 112+/-10 ml/kg per h in dexamethasone-treated females). There were no differences in body weight or weights of the kidney and heart between the treatments in both females and males.In conclusion, these results are reassuring for patients similarly exposed to prenatal dexamethasone treatment for CAH, as in our animal model no evidence of altered renal function or predisposition to adult hypertension was found.
M. L. WIEDMAN, F. W. DUNIHUE, and W. VAN B. ROBERTSON
The effect of combinations of normal, low and high sodium chloride intake with normal, low and high mineralocorticoid level on granularity of cells in the juxtaglomerular apparatus has been studied in the rat. The results have been compared with previously reported data from a similar series in the cat. With one exception, low sodium intake by normal rats, the granular cell index in both rat and cat was inversely related to the mineralocorticoid level and unrelated to the sodium intake. Data are presented which suggest that this exception is only apparent and may be explained on the basis of a different adrenal response by the rat.
Maria-Christina Zennaro, Sheerazed Boulkroun, and Fabio Fernandes-Rosa
Primary aldosteronism (PA) is the most common and curable form of secondary hypertension. It is caused in the majority of cases by either unilateral aldosterone overproduction due to an aldosterone-producing adenoma (APA) or by bilateral adrenal hyperplasia. Recent advances in genome technology have allowed researchers to unravel part of the genetic abnormalities underlying the development of APA and familial hyperaldosteronism. Recurrent somatic mutations in genes coding for ion channels (KCNJ5 and CACNA1D) and ATPases (ATP1A1 and ATP2B3) regulating intracellular ionic homeostasis and cell membrane potential have been identified in APA. Similar germline mutations of KCNJ5 were identified in a severe familial form of PA, familial hyperaldosteronism type 3 (FH3), whereas de novo germline CACNA1D mutations were found in two cases of hyperaldosteronism associated with a complex neurological disorder. These results have allowed a pathophysiological model of APA development to be established. This model involves modifications in intracellular ionic homeostasis and membrane potential, accounting for ∼50% of all tumors, associated with specific gender differences and severity of PA. In this review, we describe the different genetic abnormalities associated with PA and discuss the mechanisms whereby they lead to increased aldosterone production and cell proliferation. We also address some of the foreseeable consequences that genetic knowledge may contribute to improve diagnosis and patient care.