Possible Role Of Melatonin Research Articles

A possible role for melatonin in regulation of chick liver xanthine dehydrogenase activity

The hormone melatonin found in the pineal gland causes a striking increase in chick liver xanthine dehydrogenase. Whether the effect is direct or indirect is unknown at present. This material, however, has no observable effect when administered alone but requires the coadministration of a material such as iproniazid or harmine. While these materials are known to be monoamine oxidase inhibitors, their modes of action relative to melatonin may be quite different.

Effect of melatonin and short photoperiod on delta 4-reductase activity in liver and hypothalamus of the hamster and the rat.

SUMMARY Adult, male hamsters exposed to a photoperiod of 1 h light: 23 h darkness for either 2, 3, 4, 6, 8, or 10 weeks exhibited significantly lower testicular weights than did controls after 3 and 4 weeks of exposure to 14 h light: 10 h darkness. Liver Δ4-reductase activity was significantly decreased by 4 weeks of exposure to the short photoperiod. Exogenous melatonin decreased Δ4-reductase activity when incubated with either hamster liver (at 10−7 and 10−5 mol melatonin/l) or hamster hypothalamus (at 10−6 mol melatonin/l). In contrast, exogenous melatonin stimulated Δ4-reductase activity in preparations of rat liver (at 10−7 and 10−6 mol/l) and rat hypothalamus (at 10−9, 10−8, 10−7, and 10−6 mol/l). The possible role of melatonin in influencing the testosterone: dihydrotestosterone ratio is discussed in relation to possible regulation of gonadotrophin release.