Using specific radioimmunoassays, melatonin was quantified in the aqueous humor and serum of male pigmented rabbits adapted to 12L:12D with lights on at 06.00 h. Melatonin concentrations in the aqueous humor at 08.00 and 16.00 h were similar (mean: 5.23 pg/ml) and significantly lower than those at 22.00 and 01.00 h (mean: 22.06 pg/ml). A parallel rhythm was also demonstrated in the serum with higher melatonin concentrations (daytime mean: 75.26 pg/ml; nighttime mean: 168.94 pg/ml). We propose that the aqueous melatonin rhythm is associated with the rhythmic change in aqueous flow.
- Aqueous humor
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