GASTRIN-RELEASING PEPTIDE IS PRODUCED IN THE PREGNANT OVINE UTERUS

Our previous finding of appreciable quantities of a gastrin-releasing peptide (GRP)-like immunoreactive (GRPLI) entity in ovine fetal and ma ternal plasma led us to examine the ovine pregnant uterus as a possibl e source of this material. At term, intense immunohistochemical staini ng for GRPLI occurred in the endometrial epithelial cells, and the ter m ovine uterus also contained abundant GRP messenger RNA (mRNA). In co ntrast, GRP mRNA was not detected in fetal membranes. GRP mRNA was pre sent in the uterus on gestational day 63; a significant increase in GR P mRNA had occurred by day 100. Thereafter, levels remained elevated u ntil term, but 3 months postpartum, GRP mRNA levels were greatly reduc ed. As previous studies suggested the GRPLI entity to be of greater mo lecular size than GRP-(1-27), we deduced the primary structure of ovin e uterus GRP by sequencing a complementary DNA clone isolated from a c omplementary DNA library constructed from term ovine uterus polyadenyl ated RNA. Ovine uterine GRP is composed of 27 amino acid residues and has a conserved C-terminal region, similar to GRP structures in other species. We conclude that during pregnancy, the ovine uterus produces considerable quantities of GRP, which may play an important but hither to unrecognized role in utero-placental development and possibly in fe tal development after transfer to the fetus.