Flow of Uterine Blood, and the Œstrous Cycle

Abstract

ALTHOUGH much has been written describing vasular changes in the endometrium with the œstrous cycle, little information is available regarding the changes in flow of blood to the whole uterus, which is largely myometrium, during this cyclic physiological event. Recently, it has been demonstrated that the fraction of an intravenously administered physiological dose of tritiated-epinephrine which is taken up from the circulation and bound in the uterus varies more than 4-fold between œstrus and diœstrus¹. Since tritiated-epinephrine is rapidly removed from the circulation, such a change could be a consequence of an alteration in the fraction of the administered catecholamine which is delivered to this organ. Sapirstein's method² was used to evaluate the fraction of the cardiac output which perfuses the uterus at various times in the œstrous cycle. (The legitimacy of applying this method for determining uterine blood flow was confirmed by demonstrating that, during the first minute after injection of potassium-42, there was no dependence of uterine uptake upon time, despite continuing recirculation of the indicator².) It will be shown that during all phases of the œstrous cycle the uterus receives 0.2–0.3 per cent of the cardiac output.