The influence of calcium-free EGTA solution upon membrane permeability in the crystalline lens of the frog

Potential difference, resistance, cation content, and ⁸⁶Rb efflux were measured in frog lenses maintained in normal or calcium-free EGTA Ringer’s solution. Exposure of the lens to calcium-free solution resulted in a rapid fall in potential and resistance, together with a twofold increase in Rh efflux rate. These rapid changes were not due to an alteration in cation distribution between the lens and its environment. However, the alteration in ⁸⁶Rb efflux rate could be explained on the basis of the fall in potential. These findings suggested that removal of calcium from the bathing medium caused a rapid increase in sodium permeability alone. This suggestion was substantiated by the results of experiments where the response of the lens to low calcium solution was determined in a medium in which 90% of the sodium had been replaced by sucrose.