The Metabolism of Estrogens in the Ewe1

No assayable quantities of estrogen from an endogenous source were found in 100-ml. samples of ewes' blood. When a microcrystalline suspension of estradiol was injected intravenously in relatively large quantities, none was found in the blood. It was suggested that the microcrystals had been phagocytized and thus removed from the circulation within 5 minutes or less. The sodium salt of estradiol, when injected intravenously, was readily extractable from 100-ml. samples of ewes' blood if it were first partially hydrolyzed in an NaOH solution. This indicated that a large percentage of the estradiol was bound very rapidly to the blood proteins. Both the sodium salt of estradiol and the microcrystalline suspension when added intravenously, had similar excretion patterns, with the microcrystalline suspension appearing in the urine at twice the excretion rate of the sodium salt of estradiol and remaining at higher rates throughout the period of collection.