The rhodopsin content of the human eye

The content of rhodopsin in the human retina was determined using a radioimmunoassay which measures both rhodopsin and opsin. A value of 0.5 nmole of rod visual pigment per mg of extractable protein was obtained, corresponding to 3.94 +/- 0.17 (mean +/- SEM, n = 42) nmole per eye. This value is slightly higher than those previously reported which were based on spectral determinations measuring only native rhodopsin. No significant difference was seen in the population studied with respect to age or sex. Human rhodopsin was partially purified by affinity chromatography on concanavalin A, and some of its properties were studied. A comparison of the immunological reactivity of human, bovine, rat and chicken rhodopsin indicated similarity among the three mammalian species, while the chicken was some 50 fold less reactive.