The Transport of Prolactin by Human Fetal Membranes*

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Abstract
The transport of PRL across human fetal membranes in vitro was studied in Lucite chambers divided by pieces of fresh fetal membranes. The transport of radiolabeled PRL from the medium bathing the decidual surface of the membranes (maternal) across the chorion to the amniotic side of the membranes (fetal) was less than 3% of the total [125I]PRD added to the medium during 2 h of incubation. A similar result was obtained for tracer moving from the amniotic to the maternal side of the membrane. During a similar period o time, 40% of the total radioimmunoassayable PRL originating from within the decidual tissue was released from the tissue and crossed the chorion to the medium bathing the amniotic surface. In the presence of cycloheximide, both the PRL released into the medium and the PRL contained within the tissue were significantly reduced. Colchicine inhibited the transport of PRL from within the decidual tissue without affecting the tissue content ofPRL. The presence or absence of the amnion did not alter these results. We conclude that 1) exogenous PRL added to the medium bathing the maternal surface of human fetal membranes does not cross th chorion to the fetal side to any significant extent, 2) PRL contained within th decidual tissue itself is released in large quantity during incubation and crosses the chorion to the amniotic side readily, and 3) the transport of decidual PRL across the chorion requires active protein synthesis and an intact microtubule system. These results in addition to previous observations lead us to conclude that the decidua is the major source of PRL in human amniotic fluid. (J Clin Endocrinol Metab52: 220, 1981)