Effect of strong illumination on the ion efflux from the isolated discs of frog photoreceptors.

(1) Low levels of illumination do not modify the efflux of the radioisotopes 22Na, 86Rb, 36Cl, and 45Ca from the isolated discs of the photoreceptors of the frog (Rana Catesbeiana). (2) The effluxes of 22Na+, 86Rb+ and 36Cl- increase when the discs are illuminated with more than 10(4) erg/cm2 per s for a few minutes. There is no effect on the efflux of 45Ca2+ or of [14C]urea. (3) The effect is greater for monochromatic lights of wavelengths in the shorter region of the spectrum. (4) The effect is also present in bleached visual membranes.