Dehydration Increases Osteopontin Expression in Rat Kidney / 대한해부학회지

ABSTRACT

Osteopontin (OPN), is a secreted phosphoprotein that is expressed in the normal kidney. However, little is known about the role of OPN in the kidney. The purpose of this study was to establish the effect of dehydration on renal OPN expression. Dehydrated rats had free access to normal rat chow, but were deprived of water for 3 days. Kidney tissues were preserved by in vivo perfusion with paraformaldehyde-lysine-periodate (PLP) and processed for immunocytochemistry and in situ hybridization. Serum sodium concentration and urine osmolality were increased in dehydrated rats. Both OPN mRNA and protein were expressed restrictively in the descending thin limb (DTL) and papillary surface epithelium (PSE) in control kidneys. In dehydrated kidneys, there was an increase in OPN mRNA and protein expression in the thick ascending limb (TAL) as well as DTL and PSE. Electron microscopy revealed that OPN immunoreactivity in the DTL and TAL cells was located in the Golgi apparatus and in small cytoplasmic vesicles. These results demonstrate that dehydration status increases the expression of OPN in renal tubules and stimulates the secretion into the urine.