MAMMALIAN BOMBESIN AS A HORMONE IN OVINE PREGNANCY - ONTOGENY, ORIGIN, AND MOLECULAR-FORMS

Mammalian gastrin-releasing peptides (GRP) are present in female repro ductive tissues and stimulate uterine contraction and DNA synthesis in the endometrium. We set out to establish whether the GRP were likely to play a role in fetal development by measuring the fetal and materna l plasma concentrations in chronically cannulated fetal sheep from 115 days gestation to term (145 days) and for 18 days after parturition. Placental fluids and fetal urine were also obtained. In a separate ser ies of animals, uterine, placental, and fetal gut and lung tissues wer e collected. Samples were extracted in acid and assayed by radioimmuno assay, and molecular forms were characterized by high-performance liqu id chromatography. GRP were present in the decidua (>10 pmol/g), as we ll as placental, uterine, lung, and gastrointestinal tissues (all <6 p mol/g). Fetal and maternal plasma GRP were elevated compared with nonp regnant ewes, falling sharply after parturition. Placental fluids and urine also contained GRP (80-410 fmol/ml). The main molecular form in all tissues and fluids examined coeluted with porcine GRP-(18-27). GRP immunoreactivity was primarily localized to epithelial cells of the d ecidua. These data suggest that plasma GRP is probably derived from th e decidua and may play a role as a circulating hormone in ovine fetal and uterine development.