Kinetics of human cone photopigments explained with a Rushton-Henry model.

Densitrometric measurements of the regeneration of cone visual photopigments have shown effects that cannot be explained by the existing quantitative models. Regeneration from a fully bleached state seems to depend on how this state has been reached and the shape of the regeneration curve cannot be produced by a first order reaction. Rushton and Henry (1968) proposed a store of 11-cis-retinal to explain rapid regeneration after a short bleach. We elaborated this idea into a quantitative model. Regeneration after three different bleach histories and steady state behaviour of the pigments was measured using the Utrecht densitometer. The Rushton-Henry model gives a good fit to the data and is clearly superior to the classical Rushton model in describing densitometric measurements.