Abstract
Biotransformation of [3H]serotonin by cultured hamster skin to 3H-metabolites corresponding to N-acetylserotonin (NAS), melatonin, and 5-methoxytryptamine (5-MT) was demonstrated. This process was time-dependent, with the highest production of radioactive NAS and melatonin metabolites after 3 and 5 h of incubation followed by a decrease in the rate of metabolite release into the media. Conversely, the formation of radioactive metabolite corresponding to 5-MT increased gradually during skin culture, reaching the highest level after 24 h of incubation. The production of 3H-metabolites, corresponding to NAS, melatonin, and 5-MT, was stimulated by forskolin with a maximum effect of forskolin at 10 microM concentration. The gas chromatographic/mass spectroscopy analysis of the fraction eluting at the retention time of NAS standard material showed that it contained NAS, further confirming production and release of NAS into the media by hamster skin. Therefore, we conclude that mammalian skin can acetylate serotonin to NAS and postulate that the NAS is further metabolized by the skin to form melatonin which is subsequently transformed to 5-MT.
Highlights
Biotransformation of [3H]serotonin by cultured hamster skin to 3H-metabolites corresponding to N-acetylserotonin (NAS), melatonin, and 5-methoxytryptamine (5MT) was demonstrated
We have identified two isozymic forms of arylamine N-acetyltransferase, NAT-1 and NAT-2, in hamster skin of which NAT-2 catalyzed the acetylation of dopamine to N-acetyldopamine and serotonin to NAS, a direct precursor of melatonin [22]
reverse-phase high-performance liquid chromatography (RP-HPLC) Identification of Tritiated NAS, Melatonin, and 5-MT—To study the possible transformation of serotonin to melatonin by mammalian skin and further metabolism to 5-MT we used short-term skin culture system [20]
Summary
Biotransformation of [3H]serotonin by cultured hamster skin to 3H-metabolites corresponding to N-acetylserotonin (NAS), melatonin, and 5-methoxytryptamine (5MT) was demonstrated. We have identified two isozymic forms of arylamine N-acetyltransferase, NAT-1 and NAT-2, in hamster skin of which NAT-2 catalyzed the acetylation of dopamine to N-acetyldopamine and serotonin to NAS, a direct precursor of melatonin [22]. This information has formed the basis for the present studies on the synthesis and degradation of melatonin by mammalian skin
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