A new approach to measuring transepithelial potentials in the bovine lens reveals a chloride-dependent component.

A new approach was used to measure anterior and posterior potentials and resistances of the bovine lens. Segments of the anterior, central and posterior lens were studied by mounting a disc of tissue from either the front or the back of the lens in a double chamber. At 35 degrees C the isolated anterior epithelial preparation exhibited a high potential of 9 mV and a low resistance of 279 omega cm2. The lens epithelium can therefore be classified as a 'leaky' or low resistance epithelium. Amiloride, benzamil and furosemide (frusemide) all reduced the anterior transepithelial potential and increased the resistance, amphotericin B (aqueous side) abolished the potential, whereas SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid) had no effect. The posterior lens preparation was found to have a 'transepithelial' of -4 mV. This potential and a proportion of the anterior potential were not sensitive to ouabain, amiloride, furosemide, Na+ removal or raised K+, but were abolished by lowering [Cl-] and reduced by the Cl- channel blocker NPPB. We conclude that chloride plays a significant role in the maintenance of transepithelial potentials at both the anterior and posterior surfaces of the lens.