11 beta OH-progesterone affects vascular glucocorticoid metabolism and contractile response

Vascular smooth muscle (VM) contains a bidirectional isoform of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the enzyme that can metabolize endogenous glucocorticoids to their respective Il-dehydro derivatives. 11 beta OH-progesterone (11 beta OH-P), a compound that can be produced in vivo, is as potent or more potent than licorice derivatives in inhibiting renal and hepatic 11 beta-HSD. When studied in homogenates prepared from primary cultures of rat VSM, 11 beta OH-P and its derivative, 11-keto-progesterone (11-keto-P), proved to be potent, directionally specific inhibitors of vascular 11 beta-HSD. 11 beta OH-P selectively inhibited the forward dehydrogenase reaction (corticosterone-->11-dehydrocorticosterone), whereas 11-keto-P selectively blocked the reverse oxidoreductase reaction. To test the physiological effects, vascular rings were prepared from rat aorta. Rings were incubated in culture media containing either a submaximal concentration of corticosterone (10 nmol/L), -dehydrocorticosterone (100 nmol/L), 11 beta OH-P (1 mu mol/L), 11-keto-P (1 mu mol/L), or a combination of glucocorticoid and inhibitor for 24 hours. After the 24-hour incubation, rings were briefly stimulated sequentially with phenylephrine (10 nmol/L to 1 mu mol/L) and angiotensin II (1 mu mol/L). The immediate contractile response in rings incubated with both corticosterone and 11 beta OH-P was greater than in rings previously incubated with either the corticosterone or 11 beta OH-P alone (eg, response to 100 nmol/L phenylephrine in milligrams of force, mean+/-SE: corticosterone, 728+/-56, n=9; 11 beta OH-P, 325+/-105, n=4; both, 1132+/-122, n=8; corticosterone versus both, P<.01). In contrast, the immediate contractile responses to phenylephrine and to angiotensin II were attenuated in rings exposed previously to both 11-dehydrocorticosterone and 11-keto-P. Thus, 11 beta OH-P and 11-keto-P (and possibly structurally similar compounds) alter the vascular effects of glucocorticoids and may play a role in glucocorticoid-induced hypertension.