Expression of renal aquaporins and sodium transporters in neonatal rats after spaceflight

Abstract

Microgravity is an alien environment for life. For example, body fluid shift to upper body may change water handling. Aquaporins and sodium transporters were identified as major proteins involved in transepithelial water and salt transport along nephron. They were regulated in concert when urinary obstruction was performed in animals. In last year, we reported ambilateral hydronephrosis and down-regulation of AQP2 in rats which developed in space during second week of life. The aim of this study is to evaluate expression of other aquaporins (AQP1, AQP3) and sodium transporters (BSC-1, TSC, Na-K-ATPase) using immunohistochemistry. Eleven 8-day old rats were launched at these ages and nursed by their dams in the Space Shuttle Colombia (flight group: FLT) or same cage on the ground (ground control: GC) for 16 days. We observed expression of water and sodium transporters in appropriate segment in all animals by immunohistochemistry. While AQP2 was down-regulated in FLT rats, we could not find differences in expression of other aquaporins and sodium co-transporters. These results suggest that spaceflight-induced hydronephrosis shared a similar expression to hydronephrosis induced by partial unilateral ureteral obstruction. [Jpn J Physiol 55 Suppl:S230 (2005)]