Steroidogenic characteristics of a new aldosterone-stimulating factor (ASF) isolated from normal human urine

Effect of cyclosporin A on aldosterone production by dispersed rabbit adreno-capsular cells

The effect of cyclosporin A on aldosterone production by dispersed adreno-capsular cells from rabbit was examined. Cyclosporin A significantly stimulated aldosterone production at concentrations of 10(-7) M and 10(-6) M. The maximum stimulation of aldosterone production by cyclosporin A (at 10(-6) M) was comparable to that by angiotensin II at 10(-8) M). This stimulating effect of cyclosporin A on aldosterone production was not accompanied by an increase in cyclic AMP production, and was not inhibited by a calcium-channel blocker, nicardipine. These results suggest that the aldosterone-stimulating action of cyclosporin A at these concentrations is not mediated by a known second messenger system such as channel-linked Ca2+ inflow or cyclic AMP.

Congenital 17 alpha-hydroxylase deficiency: a clinicopathologic study

The histopathologic features of the adrenal glands in three cases of congenital 17 alpha-hydroxylase deficiency are described in relation to clinical and endocrine findings. Diffuse or nodular adrenocortical hyperplasia, particularly in the zonae fasciculata and reticularis, was observed in all cases examined. The hyperplastic adrenal cortices were composed of cells with morphologic features of hypercorticism and hyperstimulation. Myelolipomatous lesions were detected in two cases. These morphologic findings were consistent with excessive adrenocorticotropic hormone secretion in this disorder. In all the cases examined, the plasma aldosterone concentration was within normal limits, and plasma renin activity was suppressed prior to dexamethasone treatment. Morphologically, however, hyperplasia of the cells with abundant mitochondria and smooth endoplasmic reticulum seemed to involve the zona glomerulosa. Nonencapsulated nests of hypertrophied cortical cells in periadrenal tissue were remarkable in one case. From these morphologic findings, we postulated hyperfunction of the zona glomerulosa as well as involvement of corticosteroids from the zona glomerulosa in the pathophysiology of this disorder.

Low-renin hypertension of childhood

Measurement of plasma renin activity (PRA) and aldosterone with a knowledge of dietary sodium balance is critical to the diagnostic evaluation of childhood hypertension. Disturbances of steroid production, regulation, metabolism and sensitivity have been implicated in the pathogenesis of low-renin hypertension in childhood. Prompt initiation of treatment is essential because the hemodynamic changes caused by long-standing hypertension may become irreversible. The clinical features and hormonal findings of the most important adrenocortical disorders associated with low-renin hypertension in childhood are summarized.

Pharmacological influences on aldosterone secretion

Besides the classical modulators of aldosterone secretion, new factors influencing positively or negatively aldosterone secretion have been described. These new factors and the effect of related drugs constitutes the aim of this review. The effect of dopamine agonists and H2-receptor antagonists on aldosterone secretion in normal volunteers as well as in different clinical situations characterized by an increased production of aldosterone opens a new field of investigation for the therapy of aldosterone secretion alterations.

Chronobiological study of factors affecting plasma aldosterone concentration in cirrhosis

We studied the mechanisms leading to derangement of aldosterone secretion in cirrhosis. The circadian patterns of plasma renin activity (PRA), aldosterone, cortisol, sodium, and potassium were studied in 16 nonazotemic cirrhotics (group 1 without ascites, 7 cases; group 2 with ascites, 9 cases) and 7 healthy controls. Group 1 did not differ from controls in aldosterone, sodium, and potassium mean daily levels (mesors), but had reduced PRA mesor (p less than 0.05). Moreover, minor derangements in circadian patterns of PRA, aldosterone, and potassium were also found. Group 2 not only showed an increased mesor of PRA (p less than 0.05), aldosterone (p less than 0.001), and reduced sodium (p less than 0.005), but also achronia in daily fluctuations of PRA, aldosterone, and potassium. In all groups the mesors of PRA and aldosterone were correlated (r greater than or equal to 0.82; p less than 0.01 or less), but the regression line slopes of patients were steeper than those of controls (group 1, p less than 0.05; group 2, p less than 0.01). Moreover, although in controls and some group 1 patients aldosterone paralleled cortisol rhythmicity, most group 2 patients had aldosterone daily patterns correlated with those of PRA. Finally, no relationships between plasma potassium and aldosterone concentrations were found in patients, whereas they were strictly related in controls. These results suggest that the renin-angiotensin system is the prevalent determinant of aldosterone secretion in cirrhosis.

Plasma immunoreactive gamma melanotropin in patients with idiopathic hyperaldosteronism, aldosterone-producing adenomas, and essential hypertension

A non-ACTH aldosterone-stimulating factor(s) has been implicated in the pathogenesis of idiopathic hyperaldosteronism (IHA). Although this factor has not been fully characterized, some evidence suggests that it may be related to a pro-gamma-melanotropin (pro-gamma-MSH), derived from the NH2-terminal region of pro-opiomelanocortin. In the present study, plasma immunoreactive (IR-) gamma-MSH levels at 0800 h in patients with IHA were evaluated (90 +/- 17 fmol/ml; range: 13-173 fmol/ml) and found to be significantly higher (P less than 0.05) than those in subjects with aldosterone-producing adenomas (33 +/- 8 fmol/ml), essential hypertension (33 +/- 6 fmol/ml), and normotensive controls (19 +/- 2 fmol/ml). Seven of nine IHA subjects had circulating IR-gamma-MSH levels above the normal range (greater than 35 fmol/ml). In plasmas sampled at 1200 h, IR-gamma-MSH was significantly higher in patients with IHA (95 +/- 26 fmol/ml) and adenomas (63 +/- 23 fmol/ml), as compared with essential hypertensives (31 +/- 6 fmol/ml) and normotensives (19 +/- 3 fmol/ml). Mean plasma IR-ACTH, plasma cortisol, and urinary cortisol levels did not differ significantly between any of these groups. In order to evaluate the effect of a pro-gamma-MSH in vitro, adrenal adenoma tissue was obtained from two patients, one with elevated IR-gamma-MSH (61 fmol/ml) and a second with low IR-gamma-MSH (12 fmol/ml). Aldosterone secretion by dispersed adenoma cells from the former, but not the latter, underwent a fourfold dose-dependent (10(-14)-10(-9) M) increase in response to human Lys-gamma 3-MSH. These data suggest that a pro-gamma-MSH may be implicated as a pathogenic factor in a subset of patients with primary aldosteronism, particularly among those differentially diagnosed as having IHA.

The effects of ACTH, serotonin, K+ and angiotensin analogues on 32P incorporation into phospholipids of the rat adrenal cortex: basis for an assay method using zona glomerulosa cells

The effects of various concentrations of serotonin, ACTH, K+, angiotensin II (AII), angiotensin III (AIII) and [Sar1]angiotensin II (SAII) on steroidogenesis and the incorporation of 32P (after preincubation to near equilibrium with the ATP pool) into phosphatidylinositol (PI), phosphatidic acid (PA) and phosphatidylcholine (PC) in a preparation of capsular cells from rat adrenals, consisting of 95% zona glomerulosa (z.g.) and 5% zona fasciculata plus reticularis (z.f.r.) cells, were investigated. Serotonin and ACTH stimulated steroidogenesis in the usual manner but had little or no effect on 32P incorporation into any of the three phospholipids. However, AII, AIII and SAII stimulated steroidogenesis and also 32P incorporation into PA and PI (maximally to about 280% of control values) but not into PC. These results taken together with other data on effects on the cAMP output and Ca2+ fluxes of z.g. cells suggest that stimulation by ACTH and serotonin is mediated by cAMP as second messenger. However, the angiotensins probably act through Ca2+, with associated changes in phospholipid metabolism. The 32P incorporation into PA as a function of lg concentration of AII was linear and showed a reasonable index of precision (0.36 +/- 0.03, eight experiments, 0.23 +/- 0.02 for a further eight experiments) and correlation with steroidogenesis. The corresponding incorporation into PI showed a maximum effect and a much poorer index of precision (1.02 +/- 0.30 (4.69 +/- 3.7] over the same full range of AII concentration used. The effects of AIII and SAII showed similar characteristics for 32P incorporation into both PA and PI, but, as for stimulation of steroidogenesis, at higher concentrations for AIII than for AII. The effects of different doses of AII, AIII and ACTH on the corticosterone output and 32P incorporation into PA, PI and PC of a preparation of cells, consisting of more than 98% z.f.r. cells, from rat decapsulated adrenals were also studied. ACTH, at low doses, which nevertheless markedly stimulated corticosterone output, had a small (maximally to about 125% of control values) but significant effect on 32P incorporation into PA, PI and PC. The maximum effect was usually at about 10(-10) M ACTH and was not significant at 10(-8) M.

Humoral responses to intracerebroventricularly administered angiotensin II in dogs

The mechanism(s) by which intracerebroventricularly administered angiotensin II (ANG II) regulates aldosterone production was investigated in dogs with chronically implanted cannula into a lateral cerebroventricle. In salt-replete and salt-depleted dogs, artificial cerebrospinal fluid (CSF) with or without ANG II (1, 10, 100 ng X kg-1 X min-1) was infused intracerebroventricularly for 2 h under pentobarbital anesthesia. Artificial CSF produced no significant humoral changes. Intracerebroventricular ANG II decreased plasma renin activity and increased both ACTH and plasma cortisol in both groups but decreased plasma aldosterone (PA) only in salt-depleted dogs. Dexamethasone pretreatment during intracerebroventricular ANG II decreased PA further in salt-replete but not in salt-depleted dogs. Moreover, the fall in PA during intracerebroventricular ANG II in salt-depleted dogs was prevented when intravenous infusion of ANG II (10 ng X kg-1 X min-1) was given simultaneously to maintain circulating ANG II levels. We conclude that PA response to intracerebroventricular ANG II is mediated primarily through the renin-angiotensin system in the salt-depleted state; however, in the salt-replete state, ACTH assumes a more important role.

Idiopathic hyperaldosteronism. A possible role for aldosterone-stimulating factor

To test the hypothesis that idiopathic hyperaldosteronism is secondary to increased adrenal stimulation by aldosterone-stimulating factor, we measured the latter in seven patients with idiopathic hyperaldosteronism and in four patients who had undergone surgical removal of an aldosterone-producing adenoma. In the patients with hyperaldosteronism, plasma aldosterone concentrations (mean +/- 1 S.E.) were 38 +/- 10 and 78 +/- 19 ng per deciliter in the supine and upright position, respectively (P less than 0.01). Supine plasma aldosterone-stimulating factor was 81 +/- 5 ng per deciliter in 15 normal subjects and 185 +/- 10 (P less than 0.01) in the patients with idiopathic hyperaldosteronism. After removal of an aldosterone-producing adenoma, plasma aldosterone-stimulating factor was normal. The supine value in each patient with idiopathic hyperaldosteronism was above the normal range (61 to 91 ng per deciliter) and increased to 290 +/- 59 ng per deciliter after four hours of upright posture. Twenty-four hour urinary excretion of aldosterone-stimulating factor was 424 +/- 35 ng (normal, 145 +/- 3; P less than 0.01) by affinity chromatography and high-pressure liquid chromatography, and it was not suppressed after two days of treatment with dexamethasone (0.5 mg orally every six hours). At the end of 48 hours, plasma concentrations were 248 +/- 40 ng per deciliter. Plasma cortisol and ACTH concentrations were under 2 micrograms per deciliter and under 40 pg per milliliter, respectively. We conclude that increased secretion of aldosterone-stimulating factor may be the cause of idiopathic hyperaldosteronism.

Development and preliminary application of a new assay for aldosterone stimulating factor

A new assay method has been developed to measure aldosterone stimulating factor (ASF) quantitatively. This method utilizes a combination of affinity chromatography and high pressure liquid chromatography (HPLC). Antibodies raised against ASF, coupled to Affi-Gel 10, were used as the affinity column, and adsorbed ASF was eluted with 4 M urea. Quantitation was based on the external standard method of analysis using the area of the standards as controls, which were previously tested by HPLC for purity. The amount of ASF in the unknown samples was calculated on the basis of the area of the peak emerging at the retention time of ASF. A parallel bioassay using adrenal glomerulosa cells was also done to assess the biological activity. In eight normal volunteers, the urinary ASF was 146 +/- 4.6 ng/24 hr urine, whereas in plasma it was 70.5 +/- 6.5 ng/100 ml. The method is reproducible, specific for ASF, and showed less than 3% inter- or intraassay variability. In a preliminary study, when ASF was quantified from the 24-hour urine of two patients with adrenal hyperplasia, a significantly higher level of ASF was found (750 and 1020 ng/24 hr urine). These data suggest that ASF may be of pathological significance in certain hypertensive patients, especially in the hypertension associated with hyperaldosteronism.

The renin-angiotensin-aldosterone system in rats of both sexes subjected to chronic hypobaric hypoxia

Plasma renin activity (PRA), plasmatic aldosterone, haematocrit, haemoglobin concentration and plasma proteins were measured in 36 Wistar rats of both sexes submitted to 380 mmHg in hypopressure chamber during 7 months and in a group of control animals (15 male and 15 female rats). PRA was significantly increased in hypoxic male (P less than 0.05) and female (P less than 0.01) rats. On the contrary, plasma aldosterone concentration did not show any significant variation. There thus was a clear dissociation between the plasmatic renin-angiotensin system and the aldosterone in rats of both sexes submitted to severe chronic hypobaric hypoxia.

Localization, purification, and biological activity of a new aldosterone-stimulating factor

An aldosterone-stimulating factor (ASF) has been isolated from normal human urine and found to be a glycoprotein with a molecular weight of 26,000 daltons. ASF stimulated aldosterone production both in vivo and in vitro. ASF was found to be different from other known aldosterone secretogogues by the use of high performance liquid chromatography (HPLC). The retention time of ASF was different (17.0 minutes) from ACTH (retention time, 28.4 minutes), beta-lipotropin (retention time, 20.5 minutes), and angiotensin II. Proteolytic enzyme digestion and purification of ASF by HPLC yielded a smaller molecule (retention time, 22.0 minutes) with a molecular weight of 4000 daltons. This smaller molecule also stimulated aldosterone production in vitro. This showed that the structural requirement for steroidogenesis may be residing in a smaller molecule. ASF failed to produce hypertension in adrenalectomized rats. By immunofluorescence (using fluorescein conjugated antibodies), ASF was found to be localized in the anterior lobe of the pituitary gland. Data suggest that ASF, a new aldosterone-stimulating hormone that has not been described before, is secreted by the pituitary gland, and the adrenal gland appears to be the target organ for the biological activities.