Hydronephrosis observed in neonatal rats after 16 days spaceflight

Abstract

Microgravity shifts body fluid to upper body during spaceflight. And the survival ratio of rat newborns after spaceflight is low, however, why newborns died in space is still unclear. They imply that the postnatal development is the key to realize generation transition in space. The aim of this study is to examine the structural development in kidney macroscopically.Eight- and 14-day old rats were launched at these ages in the Space Shuttle Colombia for 16 days (STS-90; Neurolab). Some of 8-day rats were reared on the ground for 30 more days after landing as the re-adaptation group. Six of 11 flight rats of the 8-day group showed ambilateral hydronephrosis. Despite the hydronephrosis and tubule expansion existed, it was thought that these kidneys were potentially functional in filtration process. This hydronephrosis was remained in the re-adaptation group, but it wasn't observed in the 14-day group.Here we found that spaceflight brings about acquired ambilateral hydronephrosis during the second week of life. This result suggests that the failure of urine transportation that occurs in upper urinary tract because of weightlessness. [Jpn J Physiol 54 Suppl:S242 (2004)]