Visual pigments before and after extraction from visual cells

When retinal visual cells are suspended in equal-density sucrose solution, the resulting suspensions scatter light strongly. An opal-glass technique has been adapted so that the light truly absorbed by such suspensions can be separately characterized from the light scattered by them. Using this technique the properties of visual pigments in their natural cell environments have been compared with the properties of the same pigments after they have been extracted into digitonin solution. Pigments from three species, Rana temporaria, Conger conger and Cyprinus carpio, have been studied. In all cases it has been found that there is no detectable change in the light-absorbing properties of the visual pigments when they are extracted from their natural environment into solution. The photoproducts formed when the visual pigments are bleached in situ are significantly different, however, from the photoproducts ordinarily found in extracts. This finding has important consequences for the interpretation of difference spectra obtained from visual-cell preparations—whether suspensions or intact retinae.