Alterations in the expression of the AQP family in cultured rat astrocytesduring hypoxia and reoxygenation

Aquaporins (AQPs) are a family of water-selective transporting proteins wit h homology to the major intrinsic protein (MIP) of lens [Cell 39 (1984) 49] , that increase plasma membrane water permeability in secretory and absorpt ive cells. In the central nervous system (CNS), we detected the transcripts of AQP3, 5 and 8 in addition to the previously reported transcripts of AQP 4 and 9 in astrocytes, of AQP3, 5 and 8 in neurons, of AQP8 in oligodendroc ytes, and none of them in microglia using RNase protection assay and the re verse transcription-polymerase chain reaction (RT-PCR). Hypoxia evoked a ma rked decrease in the expression levels of AQP4, 5 and 9, but not of AQP3 an d 8 mRNAs, and in astrocytes in vitro subsequent reoxygenation elicited the restoration of the expression of AQP4 and 9 to their basal levels. Interes tingly, AQP5 showed a transient up-regulation (about 3-fold) and subsequent down-regulation of its expression within 20 h of reoxygenation after hypox ia. The changes in the profiles of AQP expression during hypoxia and reoxyg enation were also observed by Western blot analysis. These results suggest that AQP5 may be one of the candidates for inducing the intracranial edema in the CNS after ischemia injury. (C) 2001 Elsevier Science BN. All rights reserved.