Phosphatidyl choline metabolism in the frog rod photoreceptor

Abstract

Using an in vitro incubation system, phosphatidyl choline metabolism was studied in the frog rod photoreceptor using [ 3H]choline as a precursor of phosphatidyl choline incorporated into the rod outer segment disc membranes. Phosphatidyl choline incorporation was not affected when visual pigment synthesis was inhibited with puromycin, but was significantly inhibited by hemicholinium, EDTA, EGTA, dinitrophenol, oligomycin and cell lysis by detergent or sonication. The presence or absence of the pigment epithelium has no effect on phosphatidyl choline metabolism other than that of a competitive nature. While neither rhodopsin, phosphatidyl ethanolamine, or phosphatidyl inositol incorporation is affected by incubation in light, phosphatidyl choline incorporation is inhibited by both prior bleaching and light incubation. Changes in the phosphatidyl choline composition of disc membranes may be one of the initial steps in the process by which rod photoreceptor outer segments shed their tips.