High activity of retinal N-acetyltransferase in the early development of the chick embryo: independence of lighting conditions.

In this paper, we studied the activities of N-acetyltransferase (NAT), hydroxyindole-O-methyltranferase (HIOMT) and melatonin content in the retina of chick embryo from the 7th day of embryonic age to hatching. Our results confirm that the dependence on lighting conditions of NAT activity and melatonin content appears to develop prior to hatching, as evidenced by differences observed when chick embryos were incubated under constant darkness or constant light. Moreover, we found high NAT activity during the first stages of the embryonic development up to 13th day of incubation. This activity, unlike late retinal NAT, is not coupled to melatonin production and is not dependent on lighting conditions.