The rate of rhodopsin regeneration in the bleached eyes of zinc-deficient rats in the dark.

Rats fed a zinc-deficient, phytate-containing diet (ZD rats) for 4 wk showed typical signs of zinc deficiency: reduced food intake, slow weight gain, a poor food efficiency ratio and subnormal zinc concentrations in the serum, femur and eye. Pair-fed, weight-matched rats fed a zinc-sufficient diet (PF rats) showed normal serum zinc values, intermediate femur zinc levels and eye zinc concentrations similar to those in ZD rats. The vitamin A status of all three groups, expressed as the concentration of vitamin A in the liver, was comparable. After extensive bleaching, the initial rate of rhodopsin regeneration in ad libitum-fed, zinc-sufficient rats (AL rats), ZD rats and PF rats was the same, whereas the extent of rhodopsin regeneration in AL rats kept in the dark for 120 min was almost twice that found in ZD and PF rats. These results are not consistent with the hypothesis that zinc deficiency primarily affects dark adaptation by reducing the activity of alcohol dehydrogenase in the eye. Rather, zinc deficiency and the generalized malnutrition that results from markedly reduced food intake seem to depress the synthesis of opsin, and probably other proteins as well, in the rod cells of the eye.