Effect of ethanol on water and chloride transport in the rat papillary collecting duct.

While it is believed that the effect of ethanol on human renal water homeostasis is indirect, amphibian membrane experiments have demonstrated direct effects albeit at high concentrations. To evaluate the direct effect of ethanol, diffusional water and chloride permeability was simultaneously measured in isolated rat papillary collecting ducts with increasing concentrations of ethanol (0, 0.12, 0.24, 0.48, 0.96 and 1.92 g%) both in the presence and absence of arginine vasopressin (AVP). Low concentration of ethanol (0.12 g%) increased basal water permeability by 9%. With increasing concentrations it then fell to control levels (0.48 g%) only to increase again with concentrations of 0.96 and 1.92 g% to a maximum increase of 26%. Similar changes in chloride permeability occurred. Water permeability in the presence of submaximal concentrations of AVP (20 microU/ml) was also significantly increased with lower concentrations of ethanol (0.12, 0.24 and 0.48 g%) but fell to control levels with higher concentrations. With the highest ethanol concentration (1.92 g%), submaximal AVP did not significantly increase water permeability. However water permeability was unaltered by increasing concentrations of ethanol in the presence of supramaximal AVP (2,000 microU/ml). These results demonstrate a direct effect of ethanol upon distal nephron water and chloride transport.