Effects of light on melatonin and two enzymes leading to its production in albino (s(al-c)) and nonalbino chickens.

A gene for sex-linked imperfect albinism in the chicken (s(al)) has been associated with increased egg production with an implication that environmental light may play a role. In this study, levels of melatonin and hydroxyindole O-methyltransferase (HIOMT) and N-acetyltransferase (NAT), two enzymes leading to melatonin production, were studied in young albino and nonalbino chickens in relation to the daily light cycle, and after 19 days of constant light or dark. Differences between genotypes were found in the levels of HIOMT activity in the pineals and retinas of birds kept in constant light for 19 days. Other measurements were not significantly different. This study would appear to show that the visual system of imperfect albino chickens reacts differently to light than that of nonalbinos, but not with changes in the daily cycle of plasma melatonin or in NAT activity, which is the enzyme primarily responsible for the control of the melatonin level in the body.