Effect of Furosemide on the Morphogenesis of Neonatal Rat Renal Papilla

Jung, Ju Young; Lim, Sun Woo; Kim, Wan Young; Han, Ki Hwan; Cha, Jung Ho; Yang, Chul Woo; Kim, Jin

Abstract

In developing rat kidney, apoptosis plays an important role in the morphogenesis of renal papilla, and hyperosmolality is well known to be one of regulating factor in apoptosis. The aim of this study was to determine the effect of hypoosmolality induced furosemide in neonate on cell proliferation and apoptosis in renal papilla. One-dayold pups were given two times a day, at 12 hour intervals, subcutaneous injection of furosemide (10 mg/kg BW) or saline for 4 days or 7days. We identified thick ascending limb by labeling with antibody to BSC1 (bumetanide-sensitive Na/K/2Cl cotransporter) and type A intercalated cell in collecting duct by labeling with antibody to band 3 protein. We also inspected apoptosis with TdT-mediated dUTP nick end labeling (TUNEL) method and cell proliferation with immunostaining for proliferating cell nuclear antigen (PCNA). The effect of hypoosmolality induced furosemide on neonatal rat kidney. 1) In furosemide-treated animals, body and kidney weights were reduced compare to control groups. the length of renal papillae of furosemide-treated groups were shortened compare to control groups. 2) Transformation from a cuboidal epithelium of thick ascending limb to a squamous epithelium of ascending thin limb in renal papilla was delayed in furosemide-treated groups. 3) In the inner medullary collecting duct of furosemide-treated groups, elimination of type A intercalated cells was delayed compared to control groups. 4) Furosemide treatment reduced the apoptotic index in transforming thick ascending limb of Henle's loop and collecting duct in renal medulla. 5) PCNA-positive cells in the transforming thick ascending limb of Henle's loop and the collecting duct in renal medulla were decreased in number in furosemide-treated groups compared to control groups. These finding suggest that renal hypoosmolality induced furosemide treatment decrease not only apoptosis but also cell proliferation and may retard renal papilla growth at least in neonatal rat kidney.