Effects Of Photoperiod On Energy Metabolism And Thermogenesis In The Melano-Bellied Oriental Vole

Seasonal changes in photoperiod is an important environmental factor for small mammals to adjust some physiological processes, such as body mass, energy metabolism and thermogenesis, for their survival. In order to further understand the adaptive physiological strategies in Melano-bellied oriental vole (Eothenomys melanogaster), integrated the changes from organism to cellular levels, we studied the responses of this specie to different photoperiods. The main results and conclusions are as follows:1. No effect was detected in body mass by 3-week photoperiod acclimation in Melano-bellied oriental vole. Compared to long photoperiod, Melano-bellied oriental vole exposed to short photoperiod showed increases in energy intake, body fat mass and percentage of body fat. Photoperiod is one of important cues to induce seasonal variations in energy balance and body fat in Melano-bellied oriental vole.2. After 3-week photoperiod acclimation, Significant effect was detected in heart wet mass and lung wet mass. No significant effects were found in other organ's wet mass and dry mass. However, short photoperiod caused increases in basal metabolic rate(BMR) and nonshivering thermogenesis(NST). Photoperiod had no effect on organ mass. Short photoperiod alone could increase thermogenic capacity in Melano-bellied oriental vole. Photoperiod is an important cue to induce seasonal variations in thermogenic capacity in Melano-bellied oriental vole.3. Residual BMR was positively related to the residual of liver wet mass, liver dry mass, heart wet mass and lung wet mass. These results indicate that there is a relationship between the sizes of internal organs and their contribution to BMR.4. Melano-bellied oriental vole exposed to short photoperiod showed increases in cytochrome c oxidase(COX) activity in liver and brown adipose tissue(BAT). Short photoperiod alone could increase thermogenic capacity. Cytochrome c oxidase(COX) activity in BAT was higher than cytochrome c oxidase(COX) activity in liver. BAT was the main thermogenic organ and took important part in thermoregulation.5. Under short photoperiod, Melano-bellied oriental vole increased the energy intake to meet the requirements of increased energy expenditure for thermogenesis. Melano-bellied oriental vole exposed to short photoperiod showed increases in BMR, NST, cytochrome c oxidase(COX) activity in liver and BAT. There were significant differences from the level of individual and the level of cell between short photoperiod row and long photoperiod row. Short photoperiod alone acted as an important signal to induce energy metabolism and thermogenesis in Melano-bellied oriental vole.In short, experiment data indicated that Melano-bellied oriental vole exhibited adaptive physiological regulations when exposed to different photoperiod. The plasticity in energy intake, BMR and NST was very important for the regulations in energy balance and thermogenesis in Melano-bellied oriental vole exposed to different photoperiod. Change in BAT COX activity and liver COX activity was cellular basis of adaptive thermogenesis. The cause and effect relationship among parameters etal needs further investigation.