Effects of androgens and antiandrogens on the inotropism induced by ouabain and isoproterenol on the left atrium of the rat in vitro

Abstract

1. 1. The effect of androgens 5β- and 5α-dihydrotestosterone (DHT, 10 −9 M), and the antiandrogens cyproterone acetate (CPA, 10 −8–10 − M), chlormadinone acetate (CMA, 10 −8–10 −6 M), medroxyprogesterone acetate (MPA, 10 −8–10 −6 M), spironolactone (SPI, 10 −5 M), flutamide (F, 10 −5 M) and cimetidine (C, 10 −5 M), on inotropic positive effect induced by ouabain (10 −8–10 −5 M) and isoproterenol (10 −8–10 −6 M), on electrically stimulated left atria of rat, has been assayed. 2. 2. Ouabain (10 −6 M) did not modify the inotropic effect of isoproterenol (10 −8–10 −6 M). 3. 3. The androgens 5β- and 5α-DHT (10 −9 M) and the antiandrogens SPI (10 −6 M), F (10 −5 M) and C (10 −5 M) inhibit the inotropic effect of ouabain and isoproterenol on electrically stimulated left atria of the rat. 4. 4. The antiandrogens CPA, MPA and CMA to 10 −7 M, inhibit the inotropic effect of ouabain. The CPA (10 −8–10 −6 M) inhibit, in a dose-dependent way the positive inotropic effect of isoproterenol. MPA and CMA (10 −8–10 −6 M) also inhibit the inotropic effect isoproterenol but the inhibitory effect is greater with 10 −8 M than 10 −6 M of both drugs. 5. 5. Taken together, our results suggest that steroidal hormones could modulate the cardiac contractility through interference with Na-pump in a non-digitalic site and/or with intracellular mediators in left atrium.