Secretion of Ethynylestradiol and Its 3-Cyclopentyl Ether in the Milk of Lactating Rats

Summary

Ethynylestradiol-6,7- 3 H(EE) or its 1 I-¹⁴C-cyclopentyl ether (EECPE) were administered to lactating rats, and the radioactivity ingested by the pups was measured during the following suckling periods: 0-4 hr; 0–24 hr; 24–48 hr. Only very small percentages of the administrered doses were found in the pups during the time intervals studied, the greatest amounts appearing during the first 4 hr after treating the mothers and the least during the 24–48 hr period. Only trace amounts of radioactivity were found in brains of the pups with most of the counts appearing in the carcasses. The radioactive compounds found in the pups were studied by column and thin-layer chromatography. In pups nursed by mothers treated with EE, EE was the only steroid which could be identified, while in pups suckled by EECPE-treated mothers, both EECPE and more polar metabolites were found. Both EE and EECPE extracted from pups were identified by crystallization to constant specific activity.