EXPRESSION OF PITUITARY PEPTIDE-23 IN THE RAT UTERUS - REGULATION BY ESTRADIOL

Peptide 23 was first identified in pituitary cell conditioned medium a s a secreted protein which was regulated in a similar fashion to growt h hormone. It was subsequently found to be a member of the C-type lect in gene superfamily and identical to pancreatis associated protein (PA P). It is widely expressed in the gastrointestinal tract. Our present study demonstrates that peptide 23 gene is also expressed in the uteru s. Peptide 23/PAP mRNA was at highest levels during estrus and was not detectable in the immature rat uterus. A single injection of 17 beta- estradiol resulted in a transient induction of peptide 23/PAP mRNA in ovariectomized rats whereas a sustained induction was seen with diethy lstilbestrol implants. In situ hybridization localized peptide 23/PAP mRNA to the luminal epithelial cells. During gestation, peptide 23/PAP mRNA was detected only in the uterine samples from day 12 to 18 of pr egnancy with maximal expression on day 12. Peptide 23 expression was c onfined to the uterus itself and not expressed in either the decidua o r the fetal tissues. PSP/reg, another closely related member of the C- lectin gene family was not expressed in any of these uterine tissues. These results indicate that estrogen may act as a physiological regula tor of peptide 23 in the uterus and suggests that this protein may hav e some role in estrogen action.