Apical membrane potentials and intracellular potassium and sodium activities in the gallbladder of the freshwater turtle mauremys caspica

Abstract

1. 1. Open-tip and liquid ion-exchanger microelectrodes were used to measure transapical membrane potential ( V a), fractional voltage ratio ( f a) and intracellular sodium and potassium activities ( a i Na, a i K) in Mauremys caspica gallbladder under open circuit conditions. 2. 2. The average values (± SEM) for V a and f a were −32 + 3 and 0.20 ± 0.03 mV respectively. 3. 3. a i Na and a i K were, respectively, 17 ± 4 and 82 + 7 mM. 4. 4. These results suggest that the mechanisms of Na + and K + transport in this tissue are essentially similar to those observed in leaky epithelia in general.