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Distribution and Regulation of Aquaporins in Intestinal Epithelial Cells

Sodium absorption and chloride secretion create osmotic gradients that drive water transport across intestinal epithelial cells. Aquaporins (AQP) are tetrameric water‐selective channels that may play an important role in facilitating transcellular water movement and maintaining physiological electrolyte balance. In the kidney, key AQPs are regulated by intracellular cAMP. We hypothesized that the cellular distribution of AQPs in the intestinal epithelium is regulated by cAMP. RT‐PCR of three intestinal epithelial cell lines demonstrated mRNA expression of: AQP1, 2, 3, and 5 in SCBN; AQP1, 2, 3, 5, 7, 8, and 9 in T84; and AQP1, 2, 3, 4, and 5 in CMT. Confocal imaging showed immunoreactivity for AQP1, 2, 3, 4, and 7 in SCBN and AQP1, 4, 6, and 9 in T84. Real time confocal live cell imaging tracked intracellular movement of GFP‐linked human AQP1 gene construct transfected into T84 cells. It suggested an increase in apical fluorescence of AQP1 within 20 min of forskolin (FSK) treatment. Cellular fractionation of CMT whole cell lysate by differential centrifugation showed a significant FSK‐dependent increase in AQP1 protein in the plasma membrane and no FSK‐induced change in the intracellular fraction. This study demonstrates that multiple AQPs are expressed in intestinal epithelial cell lines, and provides evidence for cAMP‐dependent regulation of AQP1 trafficking.