Microelectrode and short-circuiting techniques for the study of ion transport in the lens

Ion transport was studied by considering the lens as a composite asymmetrical system rather than a closed system. When the toad lens is isolated in a chamber, the anterior surface of the lens is 30 mV positive with respect to the posterior surface. Translenticular unidirectional fluxes of Na, Cl, and K were measured under short-circuit conditions. It was found that only Na is actively transported across the lens; the transport being in a posterior-anterior direction. A discrepancy between net Na flux and short-circuit-current is interpreted on the basis of Na being gained by the lens across its posterior surface and K being lost across its anterior surface. With the aid of a glass microelectrode the potential difference across the epithelial layer under the anterior capsule was determined and a larger short-circuit-current obtained. It is concluded that in the amphibian lens the movement of K appears to be secondary to electrical gradients created by an electrogenic Na pump.