ISSN:
1600-079X
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: The purpose of this study was to examine the day/night levels of pineal melatonin and its rate limiting enzyme N-acetyltransferase (NAT) in relationship to the ratio of 11-cis-to all-trans-retinal. Three-week-old chicks were placed in 12:12 light: dark (LD 12:12) cycle for one week, pineals were collected during the light phase at 1500 (i.e., after 10 hr light), during the dark phase at 1900 (i.e., 2 hr after dark), at 2100 (i.e., 4 hr after dark), and at 2300 (i.e., 6 hr after dark) and after light extension to 1900. The results show that light-sensitive 11-cis-retinal in the chick pineal has the same diurnal rhythm as NAT and melatonin; all constituents increased within 2 hr of darkness onset (at 1900) and reached their peak after 4 hr of dark. All values were lowest during the light phase at 1500. Low values for 11-cis-retinal, NAT, and melatonin were also seen in the group of chicks which experienced light extension to 1900. The data indicate that in vivo light plays a major role in triggering rhodopsin-bound 11-cis-retinal production within 2–4 hr after darkness onset; this change likely serves as the signal for the subsequent formation of the hormonal product of the pineal gland, melatonin.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1600-079X.1993.tb00519.x
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