Mechanisms for regulation of intramembranous amniotic fluid (AF) absorption: gene expression of prolactin (PRL) receptor nephrin

Abstract

FLUID (AF) ABSORPTION: GENE EXPRESSION OF PROLACTIN (PRL) RECEPTOR NEPHRIN FATANEH AMIDI, DAVE GAYLE, SAM WANG, MICHAEL ROSS, Harbor-UCLA Medical Center, Department of Obstetrics and Gynecology, Torrance, CA OBJECTIVE: Although absorption of AF across the chorioamnion (intramembranous flow) is central to AF volume regulation, little is known regarding its regulation. Nephrin-like proteins regulate transcellular protein permeability in several organs at epithelial podocytes. PRL, having watermineral hormone properties, also has a potential role in AF volume. As amnion cells have similar structures as podocytes, we postulated that Neph1 and PRL may regulate fetal chorioamnion permeability and thus influence AF volume. We sought to determine the expression of Neph1 and PRL receptor genes in rat fetal membranes and placenta. Results are compared to beta-actinmRNA levels. STUDY DESIGN: Pregnant Sprague Dawley rats (n = 3) at gestation day 18 were anesthetized and the uterus exposed. Individual placentas and fetal chorioamnion were harvested and homogenized to isolate total RNA for mRNA determinations using real time RT-PCR. RESULTS: Fetal membranes expressed high levels of neph1 mRNA which was significantly greater than placental levels ((1.3 ± 0.3 vs 0.01 ± 0.01 AU, p = 0.03). Fetal membranes also had elevated levels of PRL receptor mRNA that were higher than placenta levels (0.21 ± 0.05 vs 0.05 ± 0.03 AU, p = 0.08). CONCLUSION: These finding indicate the expression of Neph1 and PRL in fetal membranes. We postulate that Neph1 and PRL regulate fetal membrane permeability to protein and electrolytes, respectively. Alterations in expression of these genes may lead to AF volume abnormalities.