Metabolism of (4-14C)estrone by sheep erythrocytes around the time of parturition.

The metabolism of [4-14C]estrone in vitro by red blood cells of sheep in late pregnancy and after partuirition has been studied. [14C]estrone (600 ng) was incubated with 0.5 ml erythrocytes plus 0.5 ml of Krebs-Ringer phosphate buffer, pH 7.4, for 2 h at 37 degrees C in an atmosphere of air. After incubation, [3H]estrogens were added to the incubation medium as internal standards for identification and for correction for procedural losses. Metabolites were isolated and purified by chromatography, acetate derivative formation, and recrystallization to a constant 3H/14C ratio. Approximately 20% and 2% of added estrone were converted to 17beta-estradiol and 17 alpha-estradiol, respectively. The remainder was recovered unchanged. Daily measurements of 17 beta-hydroxysteroid dehydrogenase activity in erythrocytes of five ewes, over the period 8 days prepartum to 4 days postpartum, showed no significant change in activity.