Effect of cGMP and cations on the permeability of cattle retinal disks

Abstract

GMP and Na or Ca ions affect the transmembrane movements of the same pool of intradiscal ions. Extradiscal Na ions activate the efflux of intradiscal Na ions. Extradiscal Ca ions activate the efflux of intradiscal Rb ions. Na and Ca ions activate Na/Ca or Ca/Ca exchange, as previously described. cGMP activates membrane permeability for all the cations tested. The reciprocal relations between cGMP and the other pathways for ion movements through disc membranes are systematically examined. Analogies between the cGMP-activated permeability of the disc membranes and the light-sensitive conductance of the rod plasma outer membrane are discussed.