Melatonin excretion in photoperiodic mammalian and bird species: chinchilla and Japanese quail.

DOMINCHIN MF; BIANCONI S; PONZIO M.F; TURINA AV; LABUCKAS D; BUSSO J.M.

Congreso; 5th Conference of the International Society of Wildlife Endocrinology.; 2015

International Society of Wildlife Endocrinology.

Photoperiod is a powerfulsynchronizer of seasonal changes in physiology and behavior. Melatonin (Mel) isconsidered a zeitgeber for seasonal photoperiodic changes and plays a role inenergy expenditure and body mass regulation. Our studies are focused to explorethe possible influence of Mel in  stressand reproductive responses to environmental cues, in photoperiodic species suchas chinchilla (Chinchilla lanigera) andJapanese quail (Coturnix coturnixjaponica). Therefore, in order to develop a reliable non-invasive method tomonitor pineal function, our experiment was designed to generate basicinformation about melatonin excretion, determining its main route and timecourse of excretion. Labeled Mel (125I-Mel; 5µCi/male) and unlabeledMel (25µg / 100g b.w.) were intraperitoneally injected to separately housed males(n=3 in each group). Excretes were collected from each individual before (-24h)and after 125I-Mel injection (every 2 h during the first day andevery 12 h until 96 h were reached). Samples were stored at −20 ºC untilprocessing. After 125I-Mel administration in chinchilla, aradioactive peak appeared in the first urine samples (range: 2-6 hpost-excretion) and rapidly decreased; in feces, maximum radioactivity exhibiteda median of 8 h post-administration (range: 6-34 h). Most of the radioactivemetabolites were recovered in urine (median 92.65 ± 2.64%). In quail, peakexcretion occurred at 3 h (range 2- 4 h). In all birds, a second smaller peakwas observed between 8 and 12 h; total recovery was 90.57 ± 5.57%. Inconclusion, the excretion pattern was similar in males of both photoperiodicspecies. Chinchilla employed mainly urine as a route to excrete melatonin. Quailexhibited two radioactive peaks in excreta, presumably representing urine andfeces excretion. Future research is necessary to characterize excretedmetabolites of endogenous melatonin in order to develop and/or choose the appropriateimmunoassay.