Inhibition Of Aldosterone Production Research Articles

Calcium-dependent regulation of aldosterone production in isolated adrenal glomerulosa cells: effects of the ionophore A-23187.

The effect of the calcium ionophore A-23187 on the regulation of aldosterone synthesis was investigated in isolated rat adrenal glomerulosa cells. Over the concentration range of 0.1--1.0 microM, A-23187 increased aldosterone production in a dose-dependent manner, with half-maximal stimulation at approximately 0.3 microM. Stimulation of aldosterone production by A-23187 was dependent on the concentration of extracellular calcium and was not accompanied by detectable increases in cAMP production. In contrast to the stimulation of steroidogenesis elicited by A-23187 alone, the ionophore significantly inhibited the aldosterone responses to angiotensin II and potassium. In angiotensin II-stimulated cells, 0.2 microM A-23187 caused half-maximal inhibition of aldosterone production, and 2 microM A-23187 inhibited aldosterone production by about 70%. The ionophore did not affect the binding of angiotensin II to isolated glomerulosa cells and did not change the sensitivity of the cells to either angiotensin II or potassium. However, A-23187 reduced the total amount of steroid produced in response to these stimuli, most markedly when the extracellular calcium concentration was less than 0.4 mM. These results indicate that although A-23187 partially inhibits the steroidogenic responses to angiotensin II and potassium, the increases in cytosolic calcium caused by submicromolar ionophore concentrations result in stimulation of aldosterone production by adrenal zona glomerulosa cells.

State of the adrenal mineralocorticoid function in sodium deficiency accompanied by adequate or excessive water intake

Sodium deficiency has been shown to stimulate the renln-angiotensin-aldosterone system indirectly through a decrease in the extracellular fluid volume [13]. However, intravenous bulk loading with dextran solution did not inhibit aldosterone production by the adrenals in rats with sodium deficiency [4]. Whether or not drinking a large volume of water in this situation has any modifying effect on the mineralocorticold function of the adrenals has not yet been studied.

Effects of beta-lipotropin and beta-lipotropin-derived peptides on aldosterone production in the rat adrenal gland.

To investigate the role of non-ACTH pituitary peptides on steroidogenesis, we studied the effects of synthetic beta-lipotropin, beta-melanotropin, and beta-endorphin on aldosterone and corticosterone stimulation using rat adrenal collagenase-dispersed capsular and decapsular cells. beta-lipotropin induced a significant aldosterone stimulation in a dose-dependent fashion (10 nM-1 muM). beta-endorphin, which is the carboxyterminal fragment of beta-lipotropin, did not stimulate aldosterone production at the doses used (3 nM-6 muM). beta-melanotropin, which is the middle fragment of beta-lipotropin, showed comparable effects on aldosterone stimulation. beta-lipotropin and beta-melanotropin did not affect corticosterone production in decapsular cells. Although ACTH(1-24) caused a significant increase in cyclic AMP production in capsular cells in a dose-dependent fashion (1 nM-1 muM), beta-lipotropin and beta-melanotropin did not induce an increase in cyclic AMP production at the doses used (1 nM-1 muM). The beta-melanotropin analogue (glycine[Gly](10)-beta-melanotropin) inhibited aldosterone production induced by beta-lipotropin or beta-melanotropin, but did not inhibit aldosterone production induced by ACTH(1-24) or angiotensin II. Corticotropin-inhibiting peptide (ACTH(7-38)) inhibited not only ACTH(1-24) action but also beta-lipotropin or beta-melanotropin action; however it did not affect angiotensin II-induced aldosterone production. (saralasin [Sar](1); alanine [Ala](8))-Angiotensin II inhibited the actions of beta-lipotropin and beta-melanotropin as well as angiotensin II. These results indicate that (a) beta-lipotropin and beta-melanotropin cause a significant stimulation of aldosterone production in capsular cells, (b) beta-lipotropin and beta-melanotropin have a preferential effect on zona glomerulosa cells, (c) beta-melanotropin contains the active peptide core necessary for aldosterone stimulation, (d) the effects of these peptides on aldosterone production may be independent of cyclic AMP, and (e) the receptors for beta-lipotropin or beta-melanotropin may be different from those for ACTH or angiotensin II.

Inhibition of in vitro production of aldosterone by manic-depressive sera.

Serum samples from psychiatric patients were added to incubations of rat adrenal cortical cells synthesizing aldosterone. A high proportion of sera from patients with bipolar manic-depressive psychosis inhibited aldosterone production, but chronic in-patients without affective disorders gave few inhibitory sera. Inhibition was greatest in depression, lowest during normal affect. In one patient studied through 11 affective cycles the inhibitor score increased during transitions from mania to depression, showing a significant regression on time. The possible relationship of this in vitro phenomenon to the defect of aldosterone regulation in manic-depressive psychosis is discussed.

TIn vitro study of frog ( Rana ridbunda Pallas) interrenal function by use of a simplified perifusion system IV. Influence of metyrapone and aminoglutethimide upon aldosterone production

A perifusion system technique has been used to compare the effects of metyrapone (SU-4885; Ciba) and aminoglutethimide, two compounds which are known to inhibit corticosteroid biosynthesis in mammal adrenal glands, upon aldosterone output by frog interrenal tissue. Rana ridibunda adrenal fragments were continuously perifused for 13 hr with amphibian culture medium. Fractions were set apart every 5 min and aldosterone levels were measured by means of a specific and sensitive radioimmunoassay method. For doses ranging from 1 × 10 −6 to 1 × 10 −3 M, metyrapone induced a decrease in aldosterone secretion rate. The infusion of three equimolar doses (1 × 10 −5 M)_of metyrapone during three consecutive periods of 1 hr or during various times (30, 60, 150 min) within the same experiment made it possible to study the kinetics of the response of the glands. The lag period (10 min), the amplitude of the inhibition (75%), and the duration of the inhibitory effect after withdrawal of metyrapone (50 min) were almost uniform, whatever the duration of the infusion. Similar patterns were obtained using aminoglutethimide, although much higher doses (up to 100-fold) were required to inhibit aldosterone production. These results demonstrate that both metyrapone and aminoglutethimide are potent inhibitors of mineralocorticoids output in amphibia. Conversely, they suggest that a single injection of each inhibitor, in vivo, would only induce a transient and light diminution in corticosteroid secretion.

Effect of a heptapeptide angiotensin analog on aldosterone secretion in the rabbit

We examined the effects of an angiotensin III (AIII) analog, isoleucine-7 AIII (Ile7-AIII), on the steroidogenic and pressor responses to angiotensin II (AII) and AIII. AII or AIII (25 ng/kg/min) were infused alone or superimposed on an infusion of Ile7-AIII (100 ng/kg/min) in conscious male New Zealand rabbits. AII and AIII induced comparable increases in plasma aldosterone concentration, but AII exhibited significantly greater pressor effect. Ile7-AIII infusion resulted in significant inhibition of AII- but not AIII-induced steroidogenesis. Despite inhibition of aldosterone production, Ile7-AIII failed to block the pressor or renin-suppressing effect of AII. Inhibition of the steroidogenic effect of AII, but not of AII, by Ile7-AIII may be taken as evidence that adrenal stimulation by AII is direct and is not mediated by in vivo conversion to the heptapeptide. The ability of the heptapeptide analog to block aldosterone stimulation by the octapeptide AII suggests that adrenal receptors may, however, have a greater affinity for the heptapeptide.

Reduced Response of Plasma Aldosterone to Acute ACTH Stimulation during Long-Term Treatment with Spironolactone in Essential Hypertension

The response of plasma aldosterone (PA) to ACTH administration (250 micrograms alpha 1-24 ACTH i.m.) before and during treatment with spironolactone (Sp, 75--100 mg/day) for at least 8 months was studied in 11 patients with essential hypertension. These responses were compared with those before and during prolonged treatment with hydrochlorothiazide (Th, 50--75 mg/day), with or without potassium supplement, in 14 hypertensives. PA and plasma cortisol (PC) were determined by radioimmunoassay in which Sp showed minimal cross-reactivity. Both Sp and Th treatments caused similar increases in plasma renin activity accompanied by nearly identical decreases in blood pressure and body weight. PA was also increased by both treatments, but to a significantly greater extent in the Sp-treated group. Serum potassium concentration was increased only by Sp treatment. The response of PA, but not of PC, to acute ACTH stimulation was blunted in the Sp-treated group. That is, the maximal increment of PA above the baseline level was significantly lower during Sp treatment than either before Sp treatment of during Th treatment. These results demonstrate that long-term treatment with Sp can inhibit aldosterone production by acute ACTH stimulation in patients with essential hypertension.

Further studies on the relationship between potassium and sodium levels and adrenocortical activity.

Steroid production in vitro by dog adrenal cortical slices was measured in the presence of varying concentrations of sodium and potassium ions. Increasing concentrations of potassium produced a significant increase in the intracellular potassium content and in the rate of synthesis of aldosterone. However, the potassium effect on aldosterone secretion may also occur without changes in tissue potassium content. Ouabain significantly diminished intracellular potassium content, but inhibited aldosterone production only at the high dose of 2.5 X 10(-3) M in the presence of an elevated external potassium level. Physiological changes in sodium concentration can modify aldosterone production. The effect was observed with changes as small as 10 mEq/liter sodium. Changes in external potassium and sodium levels modulate aldosterone as well as corticosterone, but not cortisol production. No changes in the intracellular content of potassium were detectable in angiotensin-stimulated tissue. Nevertheless, high doses of ouabain blocked angiotensin-stimulated aldosterone production without affecting cortisol production. The dissociation observed between intracellular potassium levels and aldosterone production suggests that there is not a simple relationship between the two parameters.

Receptor binding of angiotensin II and antagonists. Correlation with aldosterone production by isolated canine adrenal glomerulosa cells.

The binding properties of the angiotensin II receptors of the adrenal cortex have been studied in isolated cells prepared by collagenase dispersion of the zona glomerulosa of the canine adrenal gland. Such cell preparations are responsive to physiological concentrations of angiotensin II, and permit correlation of binding of angiotensin II and its analogues with aldosterone production in vitro. Uptake of 125I-angiotensin II (5 X 10(-11) M) by glomerulosa cells at 37 degrees C reached a steady state at 45 minutes, with a subsequent plateau for at least 60 minutes. Angiotensin II binding was also dependent upon the hormone and cell concentrations employed during uptake studies. Bound angiotensin II was rapidly dissociated from canine adrenal cells after addition of the unlabeled octapeptide. High affinity sites with equilibrium association constant (Ka) of 3.3 X 10(9) M-1 comprised 25-33% of the receptor population and the remainder of the sites were of lower affinity, 2.5 X 10(8)M-1. Binding of angiotensin II analogues and antagonists was found to be consistent with their biological activities. The analogue most extensively evaluated was [Sar-1]angiotensin II, which exhibited enhanced binding activity when compared to angiotensin II, and had a higher equilibrium association constant by kinetic analysis and direct binding studies. Direct binding of labeled angiotensin II to the adrenal glomerulosa receptor has been correlated with a progressive response in aldosterone production. The steroidogenic response to angiotensin II was maximal when 25% of the receptor population was occupied; this fraction corresponds to the proportion of high affinity receptor sites measured by binding analysis. In addition, inhibition of angiotensin II binding to receptor sites by the competitive antagonist [Sar-1, Ala-8]angiotensin II has been correlated with inhibition of aldosterone production. These findings serve to demonstrate the biological significance of the angiotensin II binding sites of the adrenal cortex, and confirm their role as receptors which mediate the steroidogenic responses to angiotensin II.

Aldosterone production by sheep adrenal glands in vitro

A novel technique for the preparation of adrenal tissue from large animals (sheep) is presented. Multiple adrenal cortex biopsies are taken using a 2 mm dia. dermatological punch and homogeneous pools of 10 tissue cylinders (1 from each gland) were incubated. Aldosterone, corticosterone and cortisol in the incubation medium were measured by double isotope derivative dilution assay. The mean within-incubation coefficient of variation of aldosterone production was 15.8%, whilst between days. unstimulated aldosterone production ranged from 0.02–0.25 μg/100 mg tissue/2 h. Aldosterone production was stimulated by ACTH, angiotensin II and potassium ions, in a manner similar, but at higher doses, to that reported for sheep in vivo. Serotonin (10 −3 mol/1) inhibited aldosterone production, lower concentrations having no effect. Substrate levels of progesterone, DOC and corticosterone (25 μg/ml) stimulated aldosterone output whilst cortisol inhibited aldosterone production. The incubation system described is simple with a high degree of reproducibility and has the advantage that up to 30 comparable incubation flasks can be prepared for any incubation, thus providing a simple technique for testing possible agonists or antagonists of steroid production.

Inhibition of aldosterone production in diuretic-induced hyperaldosteronism by aldosterone antagonist canrenone in man.

Healthy male subjects orally received the diuretic thiabutazide (15 mg/day) over 3 days. Thiabutazide caused a considerable loss in sodium and fluid and thereby induced a marked secondary hyperaldosteronism. On the third day of thiabutazide treatment one half of the subjects additionally received 5 mg/kg micronized canrenone. During the experiment a moderate dietary sodium restriction and a constant fluid intake were prescribed. Canrenone caused a significant decrease in aldosterone excretion in thiabutazide-induced hyperaldosteronism. The plasma aldosterone concentration was highly significantly reduced over more than 12 hrs after the administration of canrenone, although a marked increase in sodium and fluid excretion occurred. It is concluded that the spirolactone canrenone is not only a competitive antagonist of aldosterone in the kidney but obviously also an inhibitor of aldosterone synthesis in man.

Selective inhibition of aldosterone synthesis by 11-hydroxylated spirolactone in rat adrenals.

The effect of the spirolactone SC5233 [3′-(3-oxo-17β-hydroxy-4-androstene-17α-yl)propionic acid-γ-lactone] and of the 11β-hydroxylated SC5233 on the synthesis of corticosteroids was examined in rat adrenal tissue. SC5233 markedly inhibited the production of both corticosterone and aldosterone. 11β-Hydroxy-SC5233 also inhibited markedly the production of aldosterone but only slightly that of corticosterone. 50% inhibition of aldosterone production by 11β-Hydroxy-SC5233 was obtained at a concentration of 7×10−5 M when the synthesis of corticosteroids was stimulated by dibutyryl cyclic AMP, while 50% inhibition of corticosterone production was obtained only at 4×10−4 M. In incorporation experiments a highly significant inhibition by SC5233 of the incorporation of 14C-progesterone into corticosterone, 18-hydroxycorticosterone and aldosterone was detectable in connexion with an accumulation of labelled deoxycorticosterone. In experiments with 11β-Hydroxy-SC5233 a significant inhibition of the incorporation of 14C-progesterone was shown for only 18-hydroxycorticosterone and aldosterone with a moderate accumulation of labelled deoxycorticosterone. Incorporation of 14C-progesterone into corticosterone was not affected by 11β-Hydroxy-SC5233. The results show that 11β-hydroxylated SC5233 induced a largely selective inhibition of aldosterone production; in contrast, SC5233 had an unselective inhibitory effect on the synthesis of both corticosteroids, aldosterone and corticosterone.

Pathogenesis of Bartter's syndrome.

Abstract In a patient with Bartter's syndrome (increased plasma renin, juxtaglomerular-cell hyperplasia, hyperaldosteronism and hypokalemia, but no hypertension), aldosterone excretion and secretion were increased only moderately despite marked elevation of plasma renin, presumably because of suppression of aldosterone production by hypokalemia. When the serum potassium was raised by administration of potassium chloride and spironolactone, while normal sodium balance was maintained, aldosterone excretion rose markedly. Infusion of albumin decreased plasma renin and aldosterone secretion, and restored normal sensitivity to the pressor effect of exogenous angiotensin. Suppression of aldosterone production to normal limits by administration of albumin, amino-glutethimide or dexamethasone failed to correct the hypokalemia, indicating that some factor other than hyperaldosteronism may contribute to urinary potassium wastage in this syndrome. This study and others raise the possibility that in some patients wit...

Protein synthesis and aldosterone production.

Aldosterone production was decreased as much as 88% when a variety of inhibitors of protein synthesis were incubated with rat adrenal quarters. Puromycin and cycloheximide were found to cause the most marked inhibition of aldosterone production. Corticosterone production was also inhibited although only to 24 % of control values. The data were consistent with the hypothesis that aldosterone production was blocked by the inhibition of adrenal protein synthesis. This inhibitory effect could be demonstrated after 30 min of incubation. Conversion experiments suggested that the puromycin-induced block occurred in the pathway between corticosterone and aldosterone. It was possible to overcome this block and stimulate aldosterone production by the addition of glucose-6-P and NADP+. An interesting additional finding was that corticosterone and cortisol inhibited adrenal protein synthesis when added to the incubation media. (Endocrinology 79: 955, 1966)