Comparative Metabolism of ¹⁴G-Estrone in the Rat and Guinea Pig

A marked species difference in estrogen metabolism has been observed between the rat and the guinea pig, both in vivo and in incubations with subcellular fractions of liver. Very little, if any, estrone-16-¹⁴C administered to rats appeared in the urine as the sulfate or glucosiduronate and although the liver microsomes from this species were shown to be able to conjugate estrogens with glucuronic acid, no such reaction occurred if the soluble fraction of the cell was also present. In contrast, under identical conditions, large amounts of the normal estrogen conjugates were formed by the guinea pig.