D600 increases the resistance associated with the equatorial potassium current of the lens

The effects of D600, the methoxy analog of verapamil, on a pCMPS system were studied. A major effect of D600 is to increase the resistance associated with the equatorial potassium current of the lens. The increase in resistance is statistically significant at concentrations above 200 microM. At concentrations of 25-50 microM, D600 counteracts the decrease in resistance produced by binding sulfhydryl groups with 1 microM pCMPS. This effect is similar to that produced by quinine and by a calcium-free medium, and is attributed to the prevention of an increase in the calcium-dependent conductance produced by pCMPS.