Graham W. Souness

Possible endogeneous regulators of steroid inactivating enzymes and glucocorticoid-induced Na+ retention

Various endogenous substances which bear similar structural resemblances to glycyrrhetininc acid were screened for inhibitory activity against 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) and 5 beta-reductase (5 beta-R). Among the compounds screened, 3 alpha, 5 beta-tetrahydroprogesterone (3 alpha,5 beta-THP) was a potent inhibitor of 11 beta-OHSD and a moderate inhibitor of 5 beta-R. Of the bile acids tested, chenodeoxycholic acid (CDCA) was the most potent inhibitor of both 11 beta-OHSD and 5 beta-R. Cholic acid (CA), a moderate inhibitor of 11 beta-OHSD was a weak inhibitor of 5 beta-R, whereas deoxycholic acid was a moderate inhibitor of 5 beta-R but a weak inhibitor of 11 beta-OHSD. 3 alpha, 5 beta-THP and bile acids were also tested to determine whether, like GA, they could confer mineralocorticoid actions upon corticosterone (B). In adrenalectomized rats pretreated with CDCA or 3 alpha,5 beta-THP, B caused a significant antinatriuresis; the effect of B plus CDCA was blocked by the antimineralocorticoid, RU 28318. Thus, we report on two structurally similar endogenous substances, 3 alpha, 5 beta-THP and CDCA, which inhibit both 11 beta-OHSD and 5 beta-R activity, and which can confer mineralocorticoid actions upon the glucocorticoid, B.

11α- and 11β-Hydroxyprogesterone, Potent Inhibitors of 11β-Hydroxysteroid Dehydrogenase, Possess Hypertensinogenic Activity in the Rat

The progesterone derivatives 11 alpha- and 11 beta-hydroxyprogesterone are potent inhibitors of 11 beta-hydroxysteroid dehydrogenase (isoforms 1 and 2) in vitro and can confer mineralocorticoid activity on corticosterone in the rat in vivo. 11 beta-Hydroxysteroid dehydrogenase metabolizes active glucocorticoids to their inactive 11-dehydro products and protects renal mineralocorticoid receptors from the high circulating levels of endogenous glucocorticoids. 11 beta-Hydroxysteroid dehydrogenase has been suggested to be important not only in the control of renal sodium retention but also of blood pressure. To assess the possible blood pressure-modulating effects of 11 alpha- and 11 beta-hydroxyprogesterone, we infused these substances into both intact and adrenalectomized Sprague-Dawley rats continuously for 14 days. Both 11 alpha- and 11 beta-hydroxyprogesterone caused a significant elevation in blood pressure within 3 days, an effect that persisted throughout the 14-day infusion. The hypertensive effects of 11 alpha-hydroxyprogesterone were abolished by adrenalectomy and significantly attenuated when 11 alpha-hydroxyprogesterone was infused together with the specific mineralocorticoid receptor antagonist RU28318. In an additional series of experiments, 11 alpha-hydroxyprogesterone significantly amplified the hypertensive effects of corticosterone in adrenalectomized spontaneously hypertensive rats but had no effects by itself in this experimental animal. These results demonstrate that both 11 alpha- and 11 beta-hydroxyprogesterone are potently hypertensinogenic in the rat and that this activity depends on an intact adrenal and at least in part on the activation of mineralocorticoid receptors. 11 beta-Hydroxyprogesterone, and similar endogenous progesterone metabolites that inhibit 11 beta-hydroxysteroid dehydrogenase, may be involved in the pathology of certain hypertensive states.

Other physiological considerations of protective mechanisms of mineralocorticoid action

Mineralocorticoid receptors (MR) are protected from the effects of endogenous glucocorticoids (GC) in mineralocorticoid (MC) target tissues such as the kidney and the parotid gland. This protection is thought to be provided by 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD). 11 beta-OHSD metabolizes cortisol (in humans) and corticosterone (B) (in the rat) to cortisone and 11-dehydro-B, their respective inactive dehydro products. We have previously shown that the antinatriuretic actions of the MC deoxycorticosterone (DOC) are amplified in carbenoxolone (CBX) treated adrenalectomized (ADX) rats. CBX is believed to inhibit 11 beta-OHSD activity; DOC, however, is not a substrate for this enzyme. We now report on 11-desoxycortisol (11-desoxy-F) and 2 alpha-methylcortisone, substances which possess no intrinsic antinatriuretic activity, are not metabolized by 11 beta-OHSD and yet cause Na+ retention in CBX-treated ADX rats. Given that none of the above steroids are substrates for 11 beta-OHSD it is unlikely that the inhibition of this enzyme is involved in the unmasking of the Na+ retention observed when these substances are given to CBX-treated animals. These results provide further evidence for an additional protective mechanism, that protects MR from the inappropriate binding of excessive amounts of endogenous MCs.

The effects of infusions of ring-a-reduced derivatives of aldosterone on the antinatriuretic and kaliuretic actions of aldosterone

Infusion of Ring-A-reduced metabolites of aldosterone in adrenalectomized male rats for 4 days revealed that 5 alpha-Ring-A-reduced derivatives, 5 alpha-dihydroaldosterone (5 alpha-DHAldo; 2.5-5.0 micrograms/day), 3 alpha,5 alpha-tetrahydroaldosterone (3 alpha,5 alpha-THAldo; 5-25 micrograms/day), and 3 beta,5 alpha-THAldo (50-175 micrograms/day) possessed intrinsic Na+-retaining activity. The same infusions of 5 alpha-DHAldo, 3 alpha,5 alpha-THAldo, and 3 beta,5 alpha-THAldo, also lowered the urinary excretion of potassium. The 5 beta-Ring-A-reduced derivative 3 alpha,5 beta-THAldo did not demonstrate either of these biological properties. In another set of experiments, on the fourth day of infusion, aldosterone (0.1 microgram/rat) was administered acutely subcutaneously; none of the Ring-A-reduced derivatives altered the Na+-retaining activity of aldosterone. However, in a dose-dependent manner, both 3 alpha,5 alpha-THAldo and 3 beta,5 alpha-THAldo blunted the urinary K+-secretory effect of aldosterone; low dosages of 5 alpha-DHAldo and larger dosages of 3 alpha,5 beta-THAldo did not. Thus, the 5 alpha-reduced derivatives of aldosterone not only lowered urinary Na+ and K+ excretion in their own right, but two of them blunted the kaliuretic response of the parent mineralocorticoid, aldosterone. Further experiments will be required to determine whether these aldosterone metabolites are further metabolized or interconverted during the expression of the regulatory properties described here and whether these properties are physiologically relevant.

11-Dehydrocorticosterone in the presence of carbenoxolone is a more potent sodium retainer than corticosterone

In vivo, corticosterone and 11-dehydrocorticosterone are interconverted in the liver and possibly kidney by 11 beta-hydroxysteroid dehydrogenase. In an effort to evaluate the relevance of this reversible reaction in relation to urinary sodium and potassium excretion, we investigated the effects of 11-dehydrocorticosterone in the presence and absence of carbenoxolone, a potent inhibitor of the oxidative component of 11 beta-hydroxysteroid dehydrogenase, and compared them with the effects of similar doses of corticosterone in carbenoxolone-treated rats. All experiments were performed on adrenalectomized male rats. Here we describe that in carbenoxolone-treated rats 11-dehydrocorticosterone and corticosterone display antinatriuretic activity, although under the conditions of this study 11-dehydrocorticosterone is a more potent sodium retainer than its parent steroid corticosterone. In addition, the antinatriuretic effects of 11-dehydrocorticosterone (like the antinatriuretic effects of corticosterone in carbenoxolone-treated rats) were blocked by the specific antimineralocorticoid RU28318.

18-substituted steroids. part 18. chemical synthesis and mineralocorticoid activity of 2α- and 2β-hydroxyaldosterone

Abstract The 2α-hydroxy and 2β-hydroxy derivatives of aldosterone have been synthesized chemically from aldosterone, after the earlier identification of 2α-hydroxylated metabolites formed in liver. Both 2α- and 2β-hydroxyaldosterone are potent mineralocorticoids, with activities on the order of 1/10 that of aldosterone on the basis of a rat bioassay. (Steroids 58 :59–63, 1993)

Antisense to Both 11β-Hsd1 and 2 Increase Glucocorticoid (GC) Activity in Vascular Tissue

P69 GC’s amplify the pressor effects of catecholamines and Ang II in VSM. Thus, the level of vasoconstriction in vascular tissue can be influenced by local GC concentrations. GC’s are metabolized to their inactive 11-dehydro derivatives by the enzyme 11β-HSD which exists in at least two isoforms, 11β-HSD1 and 11β-HSD2. 11β-HSD2 is unidirectional, with only dehydrogenase activity (inactivating GC’s) while 11β-HSD1 is bi-directional, also possessing reductase activity and thus the ability to reactivate 11-dehydroGC’s back to the active parent steroid. The aim of the present study was to investigate the role of each isoform in the regulation of GC metabolism in vascular tissue. Aortic rings (2-3mm), from male SD rats, were incubated for 24 hrs in DMEM media with either corticosterone (B) or 11-dehydrocorticosterone (11-dehydroB)(10 -8 -10 -7 M) ± specific Antisense oligos (20 μg/ring) targeted against rat 11β-HSD1 or 11β-HSD2. The contractile responses to graded doses of phenylephrine (PE; 10 -9 - 10 -6 M)in individual rings were then measured. In aortic rings co-incubated with B and 11β-HSD2 Antisense, the contractile responses to PE were amplified 30-50% versus rings incubated with B + nonsense oligonicleotide (n = 21, p