Atrial Natriuretic Peptide Receptors on the Glomerular Epithelial Cell and Their Roles in Regulation of Glomerular Ultrafiltration

点击翻译按钮获取中文摘要

Major effects of atrial natriuretic peptide (ANP) on the kidney are diuresis and natriuresis. The ANP-induced diuresis is caused by an increase of glomerular filtration rate. To understand how ANP increases glomerular filtration rate, the receptor for ANP have been localized in the kidney. The receptor was shown in the glomeruli and inner medulla by ligand binding experiments. However, recent molecular biology techniques disclosed the presence of three distinct subtypes of ANP receptors; two biological receptors (A and B) and a clearance receptor (C). In the present study, complementary RNA probes which discriminate these receptor subtypes were used to localize them individually.Ribonuclease protection assay demonstrated that mRNA for type A and type C ANP receptors were predominantly present in the glomeruli and mRNA for type A in the inner medulla. The type C receptor mRNA was found exclusively in the glomerulus and the alternative splicing of the type C mRNA was suggested by the ribonuclease protection assay. By in situ hybridization, the type A receptor mRNA was localized in the glomerular epithelial cells and the epithelial cells of inner medullary collecting tubules. These results indicate that ANP excites the glomerular epithelial cell through type A ANP receptors to increase ultrafiltration coefficient and subsequently glomerular filtration rate and propose a hypothesis that the glomerular epithelial cell plays an important role in the regulation of glomerular filtration rate.