Aquaporins increase the water permeability in many cell types across many species. We
investigated the effects of external pH and Ca 2+ on water permeability ofXenopus oocytes
injected with aquaporin cRNA by measuring the rate of swelling in hypotonic solutions.
Lowering pH to 6.5 increased the water permeability of aquaporin (AQP0) 3.4±0.4-fold.
Diethylpyrocarbonate pretreatment increased water permeability 4.2±0.5-fold and abolished
pH sensitivity, suggesting that the pH regulation is mediated by an external histidine …