The Effects Of Chronic Hypoxia On Thermoregulation And Metabolism In Phrynocephalus Vlangalii

Hypoxia can elicit an array of behavioral and physiological responses in animals ranging from protozoa to mammals. Phrynocephalus vlangalii (P. vlangalii) are widely distributed on Tibet Plateau covering large span of altitude and diverse habitats. In present study P. vlangalii were exposed to 8% oxygen concentration in hypoxic chamber for 6 weeks, the oxygen concentration of control group was 15%. Then the preferred body temperature (Tb), standard metabolic rate (SMR), heart rate and metabolic enzyme activities of the lizards were measured at 20℃ and 30℃. The results indicated that hypoxia exposure decreased preferred Tb, standard metabolic rate (SMR) and heart rate. Lactate dehydrogenase (LDH) activity of 8% O2 group became significant elevated in liver and skeletal muscle compared with control group at 20℃, but there was no significant difference at 30℃. In addition, LDH activity in heart descended significantly after hypoxic acclimatization at 20℃ and 30℃. The Q10 of LDH of 8% O2 group became significant elevated in heart, indicated that hypoxia would change heat sensitivity of LDH activity. By electrophoresis we found that LDH contains five isozymes (LDH1, LDH2, LDH3, LDH4 and LDH5) and be expressed specifically in liver, skeletal muscle and heart. The heart mainly contains LDH1 and LDH2, while liver and skeletal muscle mainly contain LDH4 and LDH5. The results show that the heart, skeletal muscle and liver have different preferences about aerobic and anaerobic metabolism. Citrate synthase (CS) activity in liver also decreased at 20℃ and 30℃. No significant difference of CS activity was found between two groups in skeletal muscle and heart. In addition, the Q10 of CS of hypoxic acclimatization group became significant elevated in skeletal muscle. Therefore, hypoxia acclimatization decreased preferred Tb and cause metabolic response.