ABSTRACT
This study is the first to analyse the daily cycle of melatonin in Dybowski’s frogs (Rana dybowskii), a species with economic importance in north-eastern China. The concentrations of melatonin in the serum, whole brain, and liver, skin, and retinal tissue samples collected from Dybowski’s frogs were measured using high-performance liquid chromatography every 4 h over a 24 h cycle. A significant melatonin peak (P< 0.05) was observed at 00:00 in the serum samples (203.25 ± 5.06 ng/L). This peak was synchronised with peak melatonin concentrations in the retinal (1513.25 ± 3.15 ng/L), liver (49.34 ± 3.67 ng/L), and whole brain (426.85 ± 6.85 ng/L) tissue samples, although melatonin concentrations in skin tissue samples peaked at 12:00 (270.02 ± 4.60 ng/L). Therefore, the time of day should be considered when examining the physiological status of this frog, given the potential effects of fluctuating daily melatonin concentrations on physiological variables.
Acknowledgments
This work was supported by the Scientific Research Project of Liaoning Provincial Education Department under Grant number LSNQN202006; the Liaoning Provincial Natural Science Foundation of China under Grant number 2019MS274; the Liaoning Province Key Research and Development Project under Grant number 2019JH8/10200018; and the earmarked fund for Modern Agro-Industry Technology Research System under Grant number CARS-48.
Disclosure of potential conflicts of interest
No potential conflict of interest was reported by the author(s).