CHANGES IN PROLACTIN RECEPTOR EXPRESSION DURING PREGNANCY IN THE MOUSE OVARY

We have isolated the cDNA encoding the cytoplasmic domain of a long fo rm of the mouse PRL receptor (PRL-R). The mRNA for this long form PRL- R and the three mRNAs encoding short mouse PRL-R that have been previo usly characterized are all expressed in both the liver and ovary. The relative amounts of these receptor forms differ between tissues, howev er. In addition, the structure of one of the short receptor forms may not be identical in the liver and ovary. Within the ovary, the abundan ce and sites of synthesis of the four PRL-R mRNAs vary during pregnanc y. Expression of the two most abundant PRL-R mRNAs increases significa ntly at midgestation. Expression of PRL-R mRNA is detected in the corp us luteum throughout pregnancy, while increased receptor mRNA levels a re evident in the granulosa cells of a subset of Graafian follicles to ward the end of pregnancy and during lactation. Some differences are a lso observed in the expression patterns of the individual receptor for ms. Most notably, one of the short form PRL-R mRNAs is uniquely detect ed in atretic follicles in early to midgestation.