Selective utilization of vitamins A1 and A2 by goldfish photoreceptors.

The rhodopsin/porphyropsin (visual pigment) ratios in the goldfish retina were induced to change over a 300-day treatment period of specified light and temperature conditions. A concomitant but much slower change in the ratios of retinyl/3-dehydroretinyl ester in the pigment epithelium (RPE) was observed. If the changes in the visual pigment ratios were dependent on the nonselective sequestering of chromophores from the RPE ester pool, then the visual pigment changes might mirror those of the esters in the RPE. However, the relatively greater rate of visual pigment changes compared to that of the RPE esters suggests that goldfish photoreceptors synthesize their visual pigment from a relatively small pool of chromophore precursor rather than from the overall pool of retinyl and 3-dehydroretinyl esters stored in the RPE.