The hypertensinogenic activity of 19-nor-deoxycorticosterone in the adrenalectomized spontaneously hypertensive rat

Infusions of 10 or 25 micrograms/day 19-nor-DOC for 2 weeks in adrenalectomized spontaneously hypertensive rats led to significant increases in blood pressure, 55 and 70 mmHg respectively. This study provides further evidence that 19-nor-DOC is a potent hypertensinogenic steroid and that the ADX SHR model is a useful, sensitive bioassay system to test for hypertensinogenic activity.     

Steroid hormone antagonism and a cyclic model of receptor kinetics

Steady state agonist-antagonist relations have been derived for a general version of a cyclic model of glucocorticoid-receptor kinetics. The model was previously shown to account quantitatively for the transient and steady state distribution of hormone-receptor complexes formed in thymus cells by several glucocorticoids. Agonist-antagonist properties of a steroid in the model are expressed quantitatively by its "agonist activity" A, the steady state ratio of nuclear-bound to total complexes it forms. For a pure agonist A = 1, for a pure antagonist A = 0. This ratio is found to be independent of steroid concentration and a function only of the rate constants of reactions involving complexes formed by the steroid. Analysis of the dependence of A on each rate constant reveals how each reaction in the cyclic model--activation, nuclear binding, dissociation of activated and nuclear-bound complexes--influences antagonist properties. The steady state interaction of an antagonist with an agonist is shown to be governed by relations that are indistinguishable from competition relations for the simplest equilibrium system, and to yield dose-response curves that are very similar to those produced by two-state allosteric models of steroid hormone antagonism, despite the fact that the cyclic model includes no allosteric mechanisms. With steroids for which relevant rate constants can be measured, the model is directly testable. Limitations of the model arise from lack of information about the nuclear events that lead to biological activity following binding of activated complexes to the nucleus.     

The response of several adrenocortical steroids to the administration of ACTH in hirsute women

Thirty-three women with hirsutism and oligomenorrhea were stimulated with synthetic adrenocorticotropin, as well as 12 controls. Of these test subjects 20 demonstrated significantly greater rises of serum levels of 3,17-dihydroxy-5-pregnen-20-one as well as dehydroepiandrosterone sulfate suggesting an attenuated deficiency of 3 beta-hydroxysteroid dehydrogenase. Five did not show similar rises of these compounds but revealed significant elevations of 17-hydroxyprogesterone as would be expected in 21-hydroxylase deficiency. None of the subjects were virilized. Eight additional hirsute women were not different than the normals. It appears that a subtle deficiency of 3 beta-hydroxysteroid dehydrogenase may be more common as an explanation of a syndrome resembling polycystic ovarian disease than has been previously recognized.     

Steroid control of steroidogenesis in isolated adrenocortical cells: molecular and species specificity

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.     

Steroid metabolism in normal and transformed liver cells. Relation with glucocorticoid antagonism

The metabolism of the potent antagonist RU38486 has been studied in cultured liver cells and in two hepatoma cell lines. In the liver cells, this steroid undergoes a rapid degradation, whereas in hepatoma cells grown in similar conditions only a minor degradation occurs. Moreover the rate of degradation is much higher for the antagonist steroid than for the agonist steroid tested, dexamethasone. The high antiglucocorticoid potency and the relative instability of the RU38486 molecule are very important to define its different effects and its mechanism of action in liver and in liver derived tumor cells. RU38486 may represent a useful drug in cancerotherapy.     

Steroid 6 beta-hydroxylase and 6-desaturase reactions catalyzed by adrenocortical mitochondrial P-450.

The minor steroid hydroxylase activity of purified bovine adrenocortical mitochondrial P-450 is described. The results indicate that both P-450scc and P-450(11 beta) act on deoxycorticosterone and androstenedione to form 6 beta-hydroxydeoxycorticosterone and 6 beta-hydroxyandrostenedione (6 beta-hydroxylase), respectively. Both forms of P-450 also catalyze 6-desaturation of androstenedione to form 4,6-androstadiene-3,17-dione (6-desaturase).     

The effect of ACTH on the plasma concentrations of the hypertensinogenic steroids, 17 alpha-hydroxyprogesterone and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one in sheep

The plasma concentrations of 17 alpha-hydroxyprogesterone (17 alpha OHP) and 17 a'20 alpha-dihydroxy-4-pregnen-3-one (17 alpha 20 alpha OHP) have been measured in sheep during 5 days of ACTH administration at 20 micrograms/kg/day a rate of infusion known to produce hypertension. Five days of ACTH administration produced a progressive increase in plasma 17OHP from 0.45 +/- 0.12 to 128.9 +/- 28.4 nmol/l and in 17 alpha 20 alpha OHP from 0.54 +/- 0.15 to 73.1 +/- 7.2 nmol/l. Calculation of the blood production rate of both steroids during ACTH treatment confirms that the rates of infusion of 17OHP (3.0 mumol/h) and 17 alpha 20 alpha OHP (1.5 mumol/h) used to produce hypertension, when infused together with the other major ovine adrenocortical steroids, produced plasma concentrations in the range as found following administration at a rate to increase blood pressure.     

Steroid regulation of monoamine oxidase activity in the adrenal medulla

Administration of different steroid hormones in vivo has distinct and specific effects on the MAO activity of the adrenal medulla. In an effort to reconstitute these effects in defined cells, we have isolated endothelial cells and chromaffin cells from the bovine adrenal medulla and tested each cell type for sensitivity to these steroids. As in the intact animal, we found that endothelial cell MAO activity was stimulated 1.5- 2.5-fold by 10 microM progesterone, hydrocortisone, and dexamethasone, inhibited by ca. 50% by 17-alpha-estradiol, but unaffected by testosterone. The type of MAO in the endothelial cells was found to be exclusively of the A type. The chromaffin cells had MAO B exclusively and were inert to treatment with dexamethasone. The mode of action of the various steroids on MAO A activity in endothelial cells seemed to be that of affecting the number of MAO molecules, as binding of [3H]pargyline, an MAO inhibitor, changed in proportion to changes in enzyme activity. Consistently, the kinetic parameters for MAO A showed changes in Vmax but not Km under all conditions. The specificity of steroid action on MAO A activity was also supported by the fact that steroid-induced changes in total cell division ([14C]thymidine incorporation) and total protein synthesis ([14C]leucine incorporation) were seen after changes in MAO A. We conclude that the differential effects of steroids on MAO activity in the intact adrenal medulla can be reproduced in cultured adrenal medullary endothelial cells but not in chromaffin cells. Therefore we suggest that the action of these steroid hormones on the intact adrenal medulla may be restricted to the endothelial cell component of this tissue.