Relation between toad bladder potassium content and permeability response to vasopressin

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Abstract
Removal of potassium from the solution bathing the serosal surface of the toad bladder is known to cause a rapid fall in short-circuit current. In the present studies, under similar conditions, there was no change in the permeability of the bladder to H2O. After 20 min. in K-free solution, cell contents of Na, K, Cl, and H2O were unchanged as was the vasopressin-stimulated flow of H2O along an osmotic gradient. However, after longer periods in K-free solution, the water permeability response to vasopressin was diminished, as was the cell K concentration and cell water content. Ouabain (10-4 [image]) in the presence of 2.5 m[image] K+ had effects similar to that of K depletion on cell electrolytes and the response to vasopressin. In experiments employing hyper- and hypotonic Ringer solution, cell K rather than cell H2O appeared to be the critical determinant of the permeability response. Since the response to cyclic 3[image],5[image]-AMP was also inhibited by K removal, the K-dependent step in the permeability response to vasopressin is probably subsequent to the production of cyclic 3[image],5[image]-AMP by the cell.