Modification of autophagic degradation by medium- and illumination conditions in frog visual cells in vitro.

In vertebrate visual cells, cytoplasmic organelles are degraded within autophagic vacuoles occurring in inner segments. In isolated frog retinas in vitro, an increase of autophagic activity as compared to in vivo controls was observed and a reduction of autophagic activity in dim red light as compared to bright white light (Remé, 1981). In this study, isolated frog retinas were superfused: (a) with and without serum addition to the superfusion medium at 400 1 X illumination; (b) without serum at 400 1 X fluorescent light or without visible light. Autophagy was significantly decreased, in cones more than in rods, in retinas superfused with serum containing medium and superfused without visible light. The increased autophagy in serum free medium is interpreted to provide precursor molecules for protein synthesis. The reduction of autophagy in darkness may reflect different functional and metabolic states of visual cells.