THE INFLUENCE OF ESTRADIOL AND CORTISOL ON UTERINE HISTAMINE OF THE OVARIECTOMIZED RAT1212

Four hours following a single intravenous dose of estradiol-17β to the ovariectomized rat, uterine histamine concentration was significantly decreased. The decrement was not due to an increase in histaminase activity in the organ. Cortisol given concomitantly did not prevent the estrogen-induced release of istamine, although it did block the uterine hydration response due to estrogen as earlier described from these laboratories. Uterine histamine concentration was restored to control levels within 14 hours following estrogen injection. Tteri taken from intact, untreated animals during those phases of the estrous cycle associated with elevated estrogen secretion exhibited histamine levels which were significantly reduced below those in the quiescent state. It is proposed that the early accumulation of water, electrolytes and plasma protein following estrogenic stimulation of the uterus are secondary manifestations of the hyperemia and increased capillary permeability resulting from estrogen-induced release of endogenous histamine.