Potassium induced changes in cell volume of gallbladder epithelium

The mechanisms of transmembrane K and anion movements were investigated by measurement of the changes in cell volume, apical membrane potential difference, and intracellular K activity resulting from exposure of Necturus gallbladder to solutions with increased K concentration. Cell swelling occurred when the tissue was exposed bilaterally to 25 mmol/l K. This swelling was both Cl and HCO3 dependent, but was not blocked by DIDS or bumetanide. Unilateral tenfold increases in extracellular K concentration did not cause cell swelling; addition of 5 mmol/l Ba to the contralateral cell surface resulted in cell volume increases comparable to those seen with bilateral K increase. Complete blockage of K channels by Ba could be demonstrated electrophysiologically at normal extracellular K concentrations but not in the presence of increased K. Our results were consistent with the passive movement of K through Ba-sensitive channels in both cell membranes. We were unable to detect other mechanisms for transmembrane K movement. The cell swelling caused by exposure to 25 mmol/l K was not due to intracellular K accumulation and may be related to the effects of membrane depolarization on voltage sensitive anion transport processes.