Abstract: AimTo study the endogenous mechanism for the inhibition of aquaporin-1 expression in rat renal proximal tubule epithelial cells in response to acetazolamide. MethodsPrimary cultured rat renal proximal tubule epithelia cells were divided into two groups: one was subjected to 1×10^-5 mol·L^-1 acetazolamide, the other served as normal control. When grown to sub-confluency, the cells were disintegrated to perform isoelectrofocusing electrophoresis in order to find the differential proteins induced by the acetazolamide treatment. The differential proteins were defined by peptide mass fingerprinting technology. ResultsTwo differential proteins were found in the cell disintegrant. The pI 3.8 protein was reduced after treatment, which showed 21.4% similarity with the brush border membrane myosin from rat brain and testis, and 27% with glycogen phosphorylase; The pI 5.5 protein was increased on the contrary, with 20% similarity to phosphatidylinositol transfer protein alpha isoform. ConclusionAcetazolamide inhibited AQP1 expression probably by affecting the expression of pI 3.8 and pI 5.5 proteins.