Steroid sex hormones, testosterone, progesterone and diethylstilbestrol, have been tested on the isolated rabbit heart. These hormones produced a negative inotropic effect (1-10 mumol/l) and an inhibitory effect on the vasopressin- or ergonovine-induced coronary spasm (0.1-10 mumol/l). Basal coronary tone was increased by testosterone and progesterone, while diethylstilbestrol induced a slight reduction of coronary perfusion pressure. The negative inotropic effect was reversed by calcium and isoprenaline, thus resembling the calcium entry blocker activity. The activation of myocardial and coronary contractility by the calcium agonist, Bay K 8644, was antagonized by all these hormones. These observations demonstrated an influence of steroid sex hormones with calcium fluxes in the isolated rabbit heart
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