Selenoprotein P expression in liver, uterus and placenta during late pregnancy.

To identify genes that exhibit increased expression in the placenta during late pregnancy, the technique of differential cDNA library screening was used to isolate a clone subsequently identified as the 3' untranslated region of the mouse selenoprotein p gene. Random primed radiolabelled cDNA probes were constructed from this clone and these probes were used to conduct Northern hybridizations against total RNA purified from mouse placenta, liver (maternal and fetal) and uterus collected sequentially during the latter third of pregnancy. Signal is present in the placenta and beginning 4 days before birth, the level of message increases, reaching maximal levels at term. The level of expression in the placenta at maximum is approximately 25 per cent of that observed in adult liver. In liver obtained from pregnant females, the level of message is increased compared to nonpregnant adults, but returns to normal shortly after birth. Message is also found in the fetal liver beginning at 4 days before birth and exhibits a pattern of expression similar to the placenta. The similarity of expression observed in fetal liver and placenta suggests a coordinated regulation of expression of this gene in these tissues. There is a minimal amount of signal present in the uterus and the expression does not appear to vary. We speculate that selenoprotein p may play a role in the transplacental transport of selenium to the fetus during late pregnancy.