TY - JOUR T1 - Ovariectomy and Estrogen-Induced Alterations in Myocardial Contractility in Female Rabbits: Role of the L-Type Calcium Channel JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 586 LP - 591 VL - 284 IS - 2 AU - Eugene Patterson AU - Lianmin Ma AU - Bela Szabo AU - Casey P. Robinson AU - Udho Thadani Y1 - 1998/02/01 UR - http://jpet.aspetjournals.org/content/284/2/586.abstract N2 - The effects of ovariectomy and estrogen replacement on myocardial contractility were examined in female rabbits. Ovariectomy failed to alter left ventricular mass, papillary muscle cross-sectional area or isometric force. Estrogen replacement after ovariectomy (0.15 μg/kg/day i.m. 17β-estradiol acetate for 7 days) increased left ventricular mass and papillary muscle mass, and reduced isometric force compared to control and ovariectomy groups. Ovariectomy did not alter increased isometric force with isoproterenol, but decreased the ED50 for Bay K8644 (compared to control and estrogen groups). Estrogen replacement increased the ED50 for isoproterenol- and Bay K8644-induced isometric force compared to control and ovariectomy groups. Ovariectomy increased and estrogen replacement decreased isometric force associated with increased Ca++o. Acute exposure to 17β-estradiol or diethylstilbesterol (10−7 M, 10−6 M) failed to alter isometric force in control papillary muscles. Estrogen replacement reduced the number, but not the dissociation constant for3H-nitrendipine binding in plasma membrane preparations (compared to ovariectomy and control groups). Peak L-type calcium currents in isolated ventricular myocytes from the three treatment groups were not significantly different. The data are consistent with an ovariectomy-induced increase and estrogen-induced decrease in L-type calcium channel density in rabbit myocardium. Estrogen-induced alterations in L-type calcium channel expression and contractility are subsequently modified by estrogen-induced cardiac hypertrophy. The American Society for Pharmacology and Experimental Therapeutics ER -