The bleaching and regeneration of rhodopsin in the cat.

1. The processes of bleaching and regeneration were monitored by retinal densitometry in living cats.2. Neither bleaching nor regeneration of rhodopsin can be described by the simple kinetic equation (Alpern, 1971) found valid for man.3. After a strong 1 min bleach, the retina contains more unbleached rhodopsin than expected on the basis of the initial bleaching rate.4. During the first 9 min after a 1 min bleach, cats regenerate rhodopsin only slowly; density changes during this period are dominated by formation and decay of metarhodopsin III. Subsequently, rhodopsin regeneration accelerates to a rate of 50%/11 min.5. No such delay precedes recovery from a prolonged (20 min) bleach.