Fetal bile salt metabolism: placental transfer of taurocholate in sheep.

Bidirectional placental transfer of taurocholate was studied in conscious, pregnant sheep near term. In studies of maternal-to-fetal transfer sodium, [14C]cholate was injected intravenously daily into the mother to label the endogenous cholate pool. Ninety-five percent of the radiolabel was present in the maternal pool as [14C]taurocholate. No radiolabel was detected in the fetal bile over 6-9 days, indicating minimal placental transfer of taurocholate to the fetus. In contrast, mean fetal-to-maternal transfer of taurocholate, studied over 3-4 days, was 2.6 mumol/24 h, representing approximately 2%/day of the fetal taurocholate pool. We conclude that in the sheep placental transfer from the mother, at term, contributes little if any taurocholate to the fetal pool. However, the placenta may be an important excretory organ for fetal bile salts, thus playing a key role in fetal steriol homeostasis.