Terence J. McKENNA

Angiotensin stimulates both early and late steps in aldosterone biosynthesis in isolated bovine glomerulosa cells

Abstract The present study was designed to examine the effect of angiotensin on both the early and the late phases of aldosterone biosynthesis. In order to isolate the early phase (the formation of pregnelone). it was necessary to identify an agent that would inhibit the 3β-hydroxysteroid dehydrogenase, 4–5 eneisomerase enzyme system which facilitates the conversion of pregnenolone to progesterone. Such an agent was found in trilostane. Treatment of zona glomerulosa cells with trilostane resulted in accumulation of pregnenolone, and the addition of angiotensin increased the accumulation of pregnenolone still further. This observation demonstrates that angiotensin stimulates aldosterone biosynthesis at a point prior to pregnenolone formation. The late phase of aldosterone biosynthesis was isolated by using aminoglutethimide to inhibit the formation of pregnenolone by cells of the zona glomerulosa. Aldosterone was formed when aldosterone precursors occurring in the biosynthetic pathway from pregnenolone onward were added. When angiotensin was added along with deoxycorticosterone, the conversion of deoxycorticosterone to aldosterone was enhanced (P

Angiotensin stimulates cortisol biosynthesis in human adrenal cells in vitro

Adrenal glands obtained from patients undergoing therapeutic adrenalectomy were used to study the effects of angiotensin on human adrenal steroidogenesis. It was observed that angiotensin stimulated cortisol biosynthesis. Although this has been demonstrated to occur in canine and bovine adrenals, angiotens in-induced cortisol biosynthesis has not been established in man. The possibility that angiotensin merely stimulated glomerulosa cells to secrete precursor steroids which accumulated in the medium and then diffused into fasciculata cells to provide substrate for cortisol biosynthesis was excluded by demonstrating that 3beta-hydroxy-5-pregnen-20-one (pregnenolone) and progesterone (the only pertinent precursors) did not accumulate in angiotensin-stimulated cell suspension. In addition, angiotensin stimulated cortisol biosynthesis in a fasciculata cell suspension in which angiotensin did not stimulate aldosterone production. Therefore, in human adrenal cell suspensions angiotensin appeared to act directly to stimulate cortisol synthesis by fasciculata cells. In normal subjects pre-treated with dexamethasone, angiotensin infusions failed to stimulate an increase in plasma cortisol. The physiological importance of angiotensin as a regulator of cortisol secretion remains, therefore, to be established.

Steroidogenesis in HCG-responsive Leydig cell tumor variants☆

Abstract Several steroids of the androgen biosynthetic pathway were measured in cell suspensions of two tumor variants originating from the gonadotropin-responsive murine M5480 Leydig cell tumor. In M5480A, the androgen-producing variant, testosterone and dihydrotestosterone were the main steroids produced basally; addition to HCG to the incubation medium resulted in increased testosterone but no change in dihydrotestosterone levels and the main steroid accumulating in the medium was progesterone. In M5480P, the progesterone-producing variant, progesterone and androstenedione were the main steroids produced, while testosterone and dihydrotestosterone production were negligible both basally and following stimulation with HCG. Progesterone levels increased more in M5480P than in M5480A with HCG stimulation. The steroid profiles observed in the M5480 tumor variants were contrasted with that of Leydig cell-enriched suspensions of normal mouse testes. Comparison of the ratios of progesterone to 17α-hydroxyprogesterone and of androstenedione to testosterone, in the two tumor variants with each other and with normal mouse testes, suggests the following alterations in steroidogenic enzymes activities: (a) a partial decrease in 17α-hydroxylase activity more marked in M5480P than in M5480A, (b) a decrease in 17β-hydroxysteroid dehydrogenase activity in M5480P. Finally, in the M5480A tumor variant, the absence of an increase in dihydrotestosterone levels with HCG stimulation suggests a decrease in 5α-reductase activity.

The binding and metabolism of testosterone by the chick oviduct

Summary A testosterone receptor was identified in cytosol from the oviducts of estrogen stimulated chicks. Testosterone binding was not detected in serum or in cytosol prepared from heart tissue. The sucrose gradient profile of the receptor was 4 S under conditions of high ionic strenght and 8 S under low ionic strength conditions. Incubation of intact oviducts at 37°C with labeled testosterone resulted in the rapid appearance of cytosol binding initially and then nuclear binding. The nuclear receptor was a 4 S protein under conditions of either high or low ionic strenght. The identity of the steroid bound to the cytosol and nuclear receptor following incubations of whole oviducts was determined by t.l.c. More than 75% of the steroid bound to the cytosol receptor was unchanged testosterone. In contrast, more than 75% of the steroid bound to the nuclear receptor was 5α-dihydrotestosterone. The observations reported in this paper indicate that testosterone binding and metabolism in the chick oviduct and in male target organs in similar.