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

DOMINCHIN, M.F.; BIANCONI, S; PONZIO, M.F.; TURINA, A. V; LABUCKAS, D.; BUSSO, J.M.

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

ISWE

Photoperiodis a powerful synchronizer of seasonal changes in physiology and behavior. Melatonin(Mel) is considered a zeitgeber for seasonal photoperiodic changes and plays arole in energy expenditure and body mass regulation. Our studies are focused toexplore the possible influence of Mel in  stress and reproductive responses toenvironmental cues, in photoperiodic species such as chinchilla (Chinchilla lanigera) and Japanese quail(Coturnix coturnix japonica). Therefore,in order to develop a reliable non-invasive method to monitor pineal function, ourexperiment was designed to generate basic information about melatonin excretion,determining its main route and time course of excretion. Labeled Mel (125I-Mel;5µCi/male) and unlabeled Mel (25µg / 100g b.w.) were intraperitoneally injectedto separately housed males (n=3 in each group). Excretes were collected fromeach individual before (-24h) and after 125I-Mel injection (every 2h during the first day and every 12 h until 96 h were reached). Samples were storedat −20 ºC until processing. After 125I-Mel administration inchinchilla, a radioactive peak appeared in the first urine samples (range: 2-6h post-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.