Differential regulation of leucine-rich primary response gene 1 (LRPR1) mRNA expression in rat testis and ovary.

In immature rat Sertoli cells, leucine-rich primary response gene 1 (LRPR1) represents a follicle stimulating hormone (FSH)-responsive gene; the function of the encoded protein is not yet known. LRPR1 mRNA expression is up-regulated very rapidly and specifically by FSH, both in cultured Sertoli cells and in vivo in regulation in more detail, in testis and ovary of fetal, immature, and adult rats. In addition, we have studied the expression of FSH receptor (FSHR) mRNA in relation to LRPR1 mRNA expression. In rat testis, LRPR1 mRNA and FSHR mRNA followed a similar expression pattern, during postnatal development and also at different stages of the spermatogenic cycle in the adult rat. Furthermore, after short-term challenge of the FSH signal transduction pathway in intact immature rats by injection with a relatively high dose of FSH, an inverse relationship between LRPR1 mRNA (up-regulation) and FSHR mRNA expression (down-regulation) was observed. Similar studies in the ovary provided completely different results. LRPR1 mRNA in the postnatal ovary is present well before expression of FSHR mRNA can be first detected. In addition, incubation of ovaries of immature rats with FSH or dibutyryl cyclic AMP (dbcAMP) did not result in up-regulation of LRPR1 mRNA expression. During fetal development, the LRPR1 mRNA expression pattern involved many more tissues, in contrast to the relatively tissue-specific expression of LRPR1 mRNA in gonads of 21 day old and adult rats. Moreover, LRPR1 mRNA expression could be detected as early as 12.5 days post-coitum, whereas FSHR mRNA is absent at this stage of fetal development. We concluded that the pronounced regulation of LRPR1 by FSH observed in the immature rat testis does not occur in the ovary. Furthermore, in the ovary LRPR1 mRNA expression does not appear to be dependent on FSH action. Finally, the LRPR1 gene product may play a general role during fetal development.