Flash photolysis of rhodopsin in the cat retina.
The bleaching of rhodopsin by short-duration flashes of a xenon discharge lamp was studied in vivo in the cat retina with the aid of a rapid, spectral-scan fundus reflectometer. Difference spectra recorded over a broad range of intensities showed that the bleaching efficacy of high-intensity flashes was less than that of longer duration, steady lights delivering the same amount of energy. Both the empirical results and those derived from a theoretical analysis of flash photolysis indicate that, under the conditions of these experiments, the upper limit of the flash bleaching of rhodopsin in cat is approximately 90%. Although the fact that a full bleach could not be attained is attributable to photoreversal, i.e., the photic regeneration of rhodopsin from its light-sensitive intermediates, the 90% limit is considerably higher than the 50% (or lower) value obtained under other experimental circumstances. Thus, it appears that the duration (approximately 1 ms) and spectral composition of the flash, coupled with the kinetic parameters of the thermal and photic reactions in the cat retina, reduce the light-induced regeneration of rhodopsin to approximately 10%.
D000818:Animals; D002415:Cats; D004307:Dose-Response Relationship, Radiation; D008027:Light; D010782:Photolysis; D012160:Retina / Q000502:physiology*; D012168:Retinal Pigments / Q000528:radiation effects*; D012243:Rhodopsin / Q000502:physiology / Q000528:radiation effects*; D013997:Time Factors
D012168:Retinal Pigments; D012243:Rhodopsin