Abstract
The transepithelial electrical potential difference was measured across hamster kidney collecting duct epithelium during antidiuresis in vivo. Measurements were obtained in free-flow, stop-flow and during luminal and peritubular perfusion with various salt solutions. The data show a significant lumen negative potential difference during free-flow, which appears to be shunted in the lower region of the papilla through the open end of the collecting ducts. Elimination of the shunt by injection of insulating material into the duct orifice raised the potential difference to an average of −34±7.7 mV (stop-flow condition). During luminal and peritubular perfusion with identical NaCl solution the potential difference averaged −55 mV. In contrast to many other epithelia it remained high, when all Na was replaced by K in the lumen compartment, but dropped to near zero upon substitution of Na by chline. During luminal perfusion with Na2SO4 the potential difference increased to −83 mV. The data suggest that the luminal membrane of collecting duct cells is permeable to both Na and K ions as well as to chloride, but that its choline and sulfate permeability is small. The main source for the potential difference appears to be active Na-transport.
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