RETINOL-BINDING PROTEIN - IMMUNOLOCALIZATION OF PROTEIN AND ABUNDANCEOF MESSENGER-RIBONUCLEIC-ACID IN CONCEPTUS AND MATERNAL TISSUES DURING PREGNANCY IN PIGS

Retinol-binding protein (RBP) is a major secretory product of Liver as well as uterine endometrium and periimplantation conceptuses of pigs. The present study examined distribution of RBP protein and abundance of RBP mRNA in pig maternal and conceptus tissues throughout pregnancy . A porcine liver RBP cDNA clone was isolated and used as probe in the se studies. Northern blot analysis detected a 1.0-1.1-kb transcript in conceptus, trophoblast, yolk sac, placenta, endometrium, myometrium, oviduct, and numerous fetal tissues. Slot blot analyses of RBP mRNA ab undance in endometrium, myometrium, conceptus, trophoblast, chorioalla ntoic placenta, and embryo/fetus indicated differential RBP gene expre ssion in each tissue. Immunocytochemical localization studies indicate d the presence of immunoreactive RBP in endometrial surface and glandu lar epithelium, circular and longitudinal muscle of myometrium, parenc hymal cells of fetal liver, and proximal convoluted tubules of fetal k idney. Results suggest an integrated system of RBP gene expression and protein secretion that allows far transport of retinol from the uteri ne endometrium to the periimplantation conceptus during early pregnanc y and to the fetal placental unit throughout pregnancy in pigs.