DEVELOPMENTAL EXPRESSION OF THE PROLACTIN RECEPTOR GENE IN RAT GONADS

The prolactin receptor (PRLR) is a member of the cytokine/prolactin/GH receptor family, and it is widely expressed in various mammalian tiss ues. Expression of the two different forms of PRLR, differing in the l ength of their cytoplasmic domains, was studied in rat gonads during f etal and postnatal development. The two forms of PRLR mRNA were analyz ed by reverse transcription (RT)-PCR using primer pairs specific for t he different forms. The specificity of the cDNA species generated by R T-PCR was verified by Southern hybridization using nested P-32-labeled oligonucleotides. The results indicated that both forms of PRLR mRNA are expressed in the rat testis and ovary, which is in agreement with previous reports. The onset of expression of the two PRLR forms occurs on day 14.5 of fetal life in rat testis. In the ovary, the long form of PRLR mRNA appears 1 day before the short form, i.e. these forms beg in to be expressed on fetal days 14.5 and 15.5 respectively. In situ h ybridization with antisense cRNA probes specific to each form of the P RLR mRNAs demonstrated specific hybridization of both forms, localized in Leydig cells from day 18.5 of fetal life and at the postnatal ages studied. Compared with our previous findings concerning the ontogeny of LH receptor gene expression, PRLR gene expression starts earlier in development and exhibits no sexual dimorphism. The presence of two fo rms of PRLR mRNA in the fetal gonads suggest that they might play diff erential roles in gonadal development and function.