The metabolism of S35-sodium estrone sulfate in the adult female rat.

In general it is considered that conjugated estrogens are less active in vivo than the free form (1). This fact is attributed generally to the slow rate of hydrolysis of the conjugated form in the body or to an increased rate of excretion; however, it was shown recently (2) that pregnant and non-pregnant rats given S35-sodium estrone sulfate by subcutaneous injection rapidly excrete S35 as inorganic sulfate in the urine and feces, indicating that this conjugated estrogen underwent rapid hydrolysis in the body. More detailed data are presented in the present paper on the rate and possible pathway of excretion of the Ss5 from Sas-sodium estrone sulfate given to adult female rats and the possible sites of hydrolysis of this conjugated estrogen.