Adaptation to water depletion in the newborn rat--immunocytochemical localization of aquaporin-2.

Little is known about the effect of prematurity on water reabsorption in the renal tubules by anti-diuretic hormone (vasopression: ADH). The purpose of this study was to assess the different mechanisms of maintaining water balance in newborn and in adult rats on ADH and aquaporin-2 (AQP2) axis. After the dehydration, the plasma ADH in newborn and adult rose 104.6% and 117.2%, respectively. In immunocytochemical study, AQP2 stained more intensively in dehydrated rats. The dehydrated adult rats apical membrane in the IMCD cells showed more intensive staining than in the control rats. Adult rats revealed more intensive staining than newborn after the dehydration in the IMCD cells. We conclude that low ADH secretion in response to dehydration might lead to inadequate production of AQP2 resulting in an increased tendency in newborn to become dehydrated.