Daily cycle of melatonin in different tissues of dybowski’s frog (Rana dybowskii)

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.

KEYWORDS:

• Melatonin
• daily cycle
• Dybowski’s frog
• Rana dybowskii

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).