The chloride effect in chicken red cone receptors

Abstract

The previously reported blue-shift of the λ max of the chicken red-absorbing cone pigment (P569) in digitonin extracts at low chloride ion concentrations has also been observed when the pigment is in situ in the outer segment membrane, both in receptor outer segment suspensions and in individual receptors. The λ max of the chloride-depleted pigment is about 506 nm, although some of the P569 form is always present and causes a variability in the λ max of the bleaching difference spectrum. The P569 and the chloride-depleted forms of the pigment can be interconverted by the simple addition or washing out of chloride ion. P569 in the receptor membrane is relatively stable in the presence of hydroxylamine at normal chloride concentrations, but reacts in the dark under ion-free conditions. Experiments with perfused excised retinae confirmed that the proportion of P569 seen in chloridecontaining suspensions is typical of those in the retina, but breakage of the receptors under ion-free conditions prevented the observation of the blue-shift of P569 in the retina.