Experimental hypertension and other responses to 18-hydroxy-deoxycorticosterone treatment in the rat.

Young female unilaterally nephrectomized, salt-loaded, Sprague-Dawley rats were treated with 200 microgram or 1 mg 18-hydroxy-deoxycorticosterone-21-acetate (18-OH-DOCA) in oil daily, and a group of kidney-intact animals on a normal salt intake was given 2 mg/day. The hormone was not found to increase saline consumption, increase urinary potassium or kallikrein excretion, or depress serum renin activity or potassium concentration. Slight hypertension did develop at 3 weeks in salt-loaded rats on the lowest dose, but this was neither increased by higher dosage or longer treatment, nor reflected by increased heart or kidney weight. The effect of 40-mg pellet implantation of DOCA and 18-OH-DOCA was then compared in unilaterally nephrectomized, salt-loaded, female Fischer 344 rats. The former caused increased saline consumption, hypertension, hypokalemia, and heart and kidney enlargement, whereas 18-OH-DOCA did not. Thus, the hypertensogenic potency of 18-OH-DOCA is, at best, a reflection of its known, very weak, mineralocorticoid activity.

Candidate genes in the regulation of Na+ transport by inner medullary collecting duct cells from Dahl rats.

Recently, we reported that primary cultures of inner medullary collecting duct cells from Dahl salt-sensitive (S) rats absorb more Na+ than do cells cultured from Dahl salt-resistant (R) rats. To begin to evaluate the molecular basis for this difference, we selected four candidate gene products that on the basis of their physiology and genetics could participate in regulation of Na+ transport by these cells. During 24-hour exposure, inhibitors of the cytochrome P450 enzymes had no effect on Na+ transport by either S or R monolayers. Twenty-four-hour exposure to NG-monomethyl-L-arginine (0.5 mmol/L), a nonspecific inhibitor of NO synthase, also had no effect on Na+ transport by either S or R monolayers. Neither atrial natriuretic peptide 1-28 (100 nmol/L) nor 8-Br-cyclic GMP (100 micromol/L) had any short-term effect on Na+ transport by either S or R monolayers. 18-Hydroxy-11-deoxycorticosterone (100 nmol/L), an adrenocorticoid hormone that is produced in greater amounts in S rats, stimulated Na+ transport by both S and R monolayers via the mineralocorticoid receptor; however, its effect was less potent than aldosterone. Congenic rats in which the R isoform of the 11beta-hydroxylase gene was bred onto the S background had monolayers that transported Na+ at a rate similar to the S rats. These results demonstrate that neither cytochrome P450 genes, NO synthase genes, the atrial natriuretic peptide receptor gene, nor the 11beta-hydroxylase gene is a likely candidate to explain the difference in Na+ transport between S and R inner medullary collecting duct monolayers in primary culture.

Evidence for an unidentified ACTH-induced steroid hormone causing hypertension.

The hypothesis that hyperaldosteronism is not the sole cause of hypertension in dexamethasone-suppressible hyperaldosteronsim was tested in an 18-year-old male. After six years of little or no treatment, the hypertension and mild hyperaldosteronism were promptly decreased by a small dose of dexamethasone. During dexamethasone treatment, when aldosterone secretion was suppressed to less than normal and he was normotensive, steroids were given by constant infusion in an attempt to reproduce the hypertension of the dexamethasone-free state. Neither five days of aldosterone or 18-hydroxydesoxycorticosterone (18-OH-DOC) at 1 mg/day, nor desoxycorticosterone (DOC) at 30 mg/day caused hypertension. However, sodium retention and potassium loss was observed during aldosterone and DOC infusion. Hypertension was produced within five days during infusion with ACTH or oral metyrapone. The hypertensive effect of the latter was abolished by addition of aminoglutethimide treatment. These studies suggest that a steroid other than aldosterone, 18-OH-DOC, or DOC may be the cause of the ACTH-induced hypertension in this patient. The aminoglutethimide data suggest that the ACTH effect on blood pressure is due to a steroid, and the metyrapone studies suggest that the steroid may be an 11-desoxysteroid. Urine and blood collected under ACTH stimulation and metyrapone treatment may be a rich source from which we may characterize this hormone.

Adrenocortical factors in hypertension. I. Significance of 18-hydroxy-11-deoxycorticosterone.

Low renin essential hypertension and the syndrome of mineralocorticoid excess have two features in common, low plasma renin activity and volume-sensitive hypertension. The proposal that both disorders share a common mechanism--because of the ability of agents that inhibit or antagonize the adrenocortical secretion to lower blood pressure in the low renin hypertensive group--appears to be based on a circular argument. The beneficial effect of removal or neutralization of the adrenocortical contribution only constitutes evidence for volume-dependency or sensitivity, which is how the low renin group is defined. Any measure that blocks a component of the normal homeostatic chain for the maintenance of extracellular and intravascular volume including the adrenal cortex would be expected to have a beneficial effect in volume-sensitive hypertension. Evidence for an adrenal factor in low renin hypertension must rest on the isolation of an active substance that reproduces the effect when readministered. 18-Hydroxy-11-deoxycorticosterone (18-OH-DOC) does not meet these criteria. It is not significantly increased in experimental hypertension and, although its overproduction in unselected low renin essential hypertensive patients remains controversial, the magnitude of the reported elevations is insufficient in relation to the low biologic activity of the steroid to account for a significant effect. Apart from its increase in the 17alpha-hydroxylase defect, 18-OH-DOC is increased in primary aldosteronism and may also be an indicator of a histologic variant of the aldosteronoma. On the basis of a large body of evidence showing parallelism between the 11beta- and 18-hydroxylase functions of the fasciculata zone, we have proposed that both enzymic functions are functionally related and may involve the same enzyme protein and catalytic site. According to this view, the secretion of 18-OH-DOC would have no special significance of its own but would be an obligatory consequence of the secretion of fasciculata zone corticosterone.

Stimulation of sodium transport by toad skin incubated with natural derivatives of corticosterone and deoxycorticosterone.

The effects on sodium transport of several steroids physiologically secreted or possibly involved in pathological disorders were compared with those of aldosterone in the isolated toad skin. The 18-hydroxylated derivatives of deoxycorticosterone and corticosterone, in contrast to their parent compounds, significantly enhanced sodium transport at a concentration of 50 nmol/l. In the presence of glucose, 18-hydroxydeoxycorticosterone increased transepithelial potential difference, as did aldosterone. The 19-nor derivative of deoxycorticosterone, recently implicated in the aetiology of adrenal regeneration hypertension, stimulated sodium transport, unlike 19-nor-corticosterone and 16-oxo-androstenediol. Insulin significantly increased sodium transport in aldosterone-treated skin and lowered the resistance. The natriferic response to vasopressin was potentiated fivefold by exposure of the skin to aldosterone and was doubled in skin exposed to 19-nor-deoxycorticosterone. We conclude that 18-hydroxylated adrenocortical steroids can play a physiological role in salt retention; furthermore, these steroids, as well as 19-nor-deoxycorticosterone, could be involved in pathological conditions such as low renin hypertension. Caution should be exercised in evaluating mineralocorticoid potency solely in terms of the urinary sodium to potassium ratio.

Aldosterone effects on water and electrolyte metabolism.

The effects of constant infusions of small doses of adrenal steroid hormones on sodium, potassium and water metabolism were studied in male adrenalectomized rats. An infusion of 1 microgram aldosterone/day was sufficient to restore normal sodium and potassium balance in a group of rats fed an unsupplemented diet. Log doses of aldosterone (0.1-10 micrograms/day for 4 days) administered some days after adrenalectomy caused linear increases in the body weight of rats fed a sodium-supplemented diet (0.05 M-NaCl as drinking fluid) during 4 days of treatment. Increases in body weight correlated with renal sodium and water balance. When steroid treatment was started at the time of adrenalectomy, sodium balance was not significantly affected although rats treated with 1 microgram aldosterone/day ate more, drank less saline, produced a smaller volume of urine of greater osmolarity and gained more weight than controls. A dose of 100 micrograms 18-hydroxy-deoxycorticosterone/day had no significant effects. Fluid intake and urine volume were not significantly affected by 1 mg corticosterone/day but food intake, water balance and weight gain were greater than controls. Rats treated with both aldosterone and corticosterone showed a decrease in free water clearance. Aldosterone and corticosterone, both singly and in combination, reduced plasma potassium levels. Plasma sodium levels were only increased when aldosterone was administered on its own. Long-term steroid infusions have revealed more about the physiology of aldosterone action than could acute measurements of renal function.(ABSTRACT TRUNCATED AT 250 WORDS)

Mineralocorticoid hypertension in childhood.

Evidence for the existence of a hormone that is stimulable by adrenocorticotropic hormone (ACTH) and capable of causing hypertension has been collected in several patients. This hormone is not a known mineralocorticoid or glucocorticoid. The hypothesis that a steroid can produce hypertension was tested in an 18-year-old man with dexamethasone-suppressible hypertension. During dexamethasone treatment, when aldosterone secretion was suppressed, less than normal and the patient was normotensive, steroids were given by constant infusion in an attempt to reproduce the hypertension of the dexamethasone-free state. Hypertension was not caused by 5 days of administration of aldosterone, 18-hydroxydeoxycorticosterone (18-OH-DOC) at 1 mg/day, or deoxycorticosterone (DOC) at 30 mg/day. However, sodium retention and potassium loss were observed during infusion of aldosterone and DOC. Hypertension was produced within 5 days during infusion of ACTH or oral metyrapone. The hypertensive effect of the metyrapone was eliminated by the additional treatment with aminoglutethimide. These studies suggest that an ACTH-dependent steroid rather than aldosterone, 18-OH-DOC, or DOC may be the cause of the hypertension in this patient. Study of a 3-year-old child who presented with short stature, hypertension, hypokalemic alkalosis, suppressed renin and ACTH, and decreased excretion of all known steroids suggested excessive secretion of a pressor hormone. Reversal of the hypertension and hypokalemic alkalosis occurred when spironolactone was administered. ACTH exacerbated the clinical and biochemical abnormalities, suggesting that the secretion of the unknown factor was dependent on ACTH. A study of the urinary steroids revealed remarkably low excretion of aldosterone and cortisol. Plasma levels of ACTH were low. The low production of aldosterone was not associated with the increased excretion of precursor metabolites. These finding suggest the secretion of an unknown hypertensive factor of remarkably high potency, with the ability to suppress the secretion of both renin and ACTH.

alpha-MSH analogues and adrenal zona glomerulosa function.

Recent studies on the control of adrenal zona glomerulosa function and aldosterone secretion have focussed attention on the role of MSH-like peptides. In particular, at low concentrations, alpha-MSH has a specific stimulatory effect on rat adrenal glomerulosa cells. The synthesis of alpha-MSH analogues which have potent and prolonged effects on melanocyte systems offers new methods of examining the specificity of this response. Two peptides were tested in which potential for a beta-turn configuration was stabilised. These were: [Nle4, D-Phe7]-alpha-MSH and the cyclic [Cys4, Cys10]-alpha-MSH. In contrast to their effects on melanocyte systems, only [Cys4, Cys10]-alpha-MSH stimulated glomerulosa cells, and it was equipotent with alpha-MSH, while [Nle4, D-Phe7]-alpha-MSH and shorter fragments had no effect when added alone. [Nle4, D-Phe7]-alpha-MSH, however, augmented the response of cells already maximally stimulated with alpha-MSH and in this respect its actions resembled those of gamma-MSH and related peptides. The augmentation produced by [Nle4, D-Phe7]-alpha-MSH and gamma 3-MSH was not additive when the two peptides were added together with alpha-MSH. The results suggest that the specificity of the alpha-MSH receptors in rat adrenal glomerulosa cells and the peptide structure-function relationships in this system are different from those described for melanocytes.

Urine electrolyte response to 18-hydroxy-11-deoxycorticosterone in normal man.

1. To assess whether the adrenal corticosteroid 18-hydroxy-11-deoxycorticosterone [18-(OH)-DOC] affects urine electrolyte excretion in normal man, seven male volunteers received 120 microgram (353 nmol) intravenously in 1 h. This was compared with glucose (50 g/l; control) and aldosterone (80 microgram, 222 nmol) infusions in the same subjects. 2. A definite though weak antinatriuretic response to 18-(OH)DOC was observed, whereas urine potassium excretion was not altered. Aldosterone increased urine potassium excretion and reduced sodium output. Urine pH was lowered by both corticosteroids, aldosterone in general having a more marked effect. Urine volume was not altered by 18-(OH)DOC. 3. Plasma concentrations of 18-(OH)DOC and aldosterone rose approximately tenfold during their respective infusions. Compared with that of aldosterone, the metabolic clearance rate of 18-(OH)DOC was slower andits plasma half-life was longer. 4. We have been able to demonstrate that 18-(OH)DOC has a definite, albeit weak antinatriuretic action in normal man, but whether or not this corticosteroid is capable of elevating the blood pressure in man remains to be shown.

Affinity of 18,19-dihydroxydeoxycorticosterone and 18-hydroxy-19-nor-deoxycorticosterone to aldosterone receptor and their mineralocorticoid activity.

Affinity of 18,19-dihydroxydeoxycorticosterone (18,19-diOH-DOC) and 18-hydroxy-19-nor-deoxycorticosterone (18-OH-19-nor-DOC) to aldosterone receptor and their mineralocorticoid activity were evaluated. 18,19-DiOH-DOC (1 X 10(-6) M) did not show appreciable binding to the receptor and its relative potency as a mineralocorticoid was estimated to be less than 1/8,000 of that of deoxycorticosterone (DOC). 18-OH-19-nor-DOC bound to the receptor with an affinity similar to that of 18-hydroxydeoxycorticosterone (18-OH-DOC) or spironolactone. Its sodium retaining activity was 0.04 times as great as that of DOC and similar to that of 18-OH-DOC.

Regulation of 11 beta/18-steroid hydroxylation in newborn rat adrenal cells in primary culture.

In newborn rat adrenal cells in primary culture, the level of activity of the 11 beta/18-steroid hydroxylase system involved in the last step of the corticosteroid biosynthesis is increased by ACTH. A parallel study of 11 beta- and 18-hydroxylation showed the same apparent Km values (64 microM) for both hydroxylations. The Vmax values differed: 11.5 micrograms/10(6) cells/h for corticosterone and 6.9 micrograms/10(6) cells/h for 18-hydroxyDOC. A dose response study of the ACTH effect, measured by the bioconversion of deoxycorticosterone to corticosterone and 18-hydroxyDOC, showed maximum hydroxylation with a dose of 2.2 mU of ACTH/ml. Addition of ACTH after several weeks in culture produced a smaller increase in 11 beta/18-hydroxylation. Removal of ACTH after several weeks of treatment produced an immediate decrease in corticosteroid production; readdition of ACTH produced an increase to the previous level in the case of the 22 mU/ml dose, but not in the case of the 2.2 mU/ml dose. The use of actinomycin D demonstrated that ACTH affects mainly the biosynthesis of protein which must be renewed approximately every 24 h. Finally, the effect of pretreatment or co-treatment with various concentrations of the end products of the reaction showed no inhibition or destruction of the 11 beta/18-hydroxylating enzyme system. Therefore, the regulation of the 11 beta/18-steroid hydroxylase system in these cell cultures seems to be accomplished through the induction by ACTH of the transcription involved in the biosynthesis of cytochrome P450(11) beta and the amount of available precursor furnished by endogenous steroidogenesis.

Effects of 18-hydroxydeoxycorticosterone on central nervous system excitability.

The effects of 18-hydroxydeoxycorticosterone (18-OH-DOC) on central nervous system excitability were studied in adrenalectomized rats. Sixty-four evoked potentials (EP) recorded from the pontine reticular formation were averaged before and after the injection of vehicle and hormone. 750 micrograms of 18-OH-DOC dissolved in 0.5 ml of a 4:1 saline Cremophor-EL solution were injected i.v. A decrease of 55.7 +/- 6.1% in the amplitude of the EPs was observed with the hormone 16.3 min +/- 2.7 (SE) after injection. Amplitude values returned to baseline levels 38 min +/- 6.8 (SE) after injection. The secretion of 18-OH-DOC is greatly increased by ACTH and might modulate central nervous system function.

Effect of intravenous infusion of corticosteroids on blood pressure, electrolytes, and water metabolism in sheep.

ACTH administration (80 IU/day for 5 days), which produces hypertension and charateristic metabolic effects in sheep (38), has been compared with the effect of intravenous infusion of cortisol (5 mg/h), corticosterone (0.5 mg/h), deoxycorticosterone (50 mug/h), and 11-deoxycortisol (1 mg/h), each given singly for 5 days. Further, a mixture consisting of aldosterone (3 mug/h), cortisol (5 mg/h), deoxycorticosterone (25 mug/h), corticosterone (0.5 mg/h), and 11-deoxycortisol (1 mg/h), was also infused intravenously for 5 days. In another series of experiments, 18-hydroxydeoxycorticosterone (100 mg/h) was also included in the combined-steroid solution. With the exception of 18-hydroxydeoxycorticosterone, which was not measured, the rates of infusionproduced peripheral arterial blood levels of the steroids similiar to those seen with ACTH stimulation. Blood pressure,water intake, urine output, and plasma and urinary electrolytes were measured: individual steroids had little effect on these, but manyof the metabolic changes produced by ATCH (hypokalemia and increased water intake andurine output) were produced by the combined-steroid infusion. However, the combined-steroid infusion failed to induce an increase in blood pressure similiar to that seen inthe ACTH experiments. Thus the findings are against a major role in ACTH hypertension for any steroid used, either singly or in combination. As yet unrecgnized factor/s may be involved in the ACTH-induced hypertension.