The Adaptation Of Lactate Dehydrogenase To Hypoxia In Phrynocephalus Erythrurus

Native Plateau animals have formed a unique genetic characteristics and mechanisms adaptation to high altitude in physiology, biochemistry, cell and molecular genetic aspects after long-term evolution. The ability to regulate the level of anaerobic metabolism of animals is important in adaptation to high altitude hypoxia. The key enzyme of anaerobic metabolism:Lactate dehydrogenase (LDH), whose structure and characteristics is a hot topic of hypoxic adaptation research. In recent years, the study of native animals anaerobic metabolism in plateau mainly focused on some native plateau mammals, including pika, yak, Tibetan antelope, but relatively little research on reptilian species.In the present study, a native plateau living lizard Phrynocephalus erythrurus which inhabit at high altitude (4353m) in Qinghai Tuotuo Rivers was chosen as an study species, and another lizard Phrynocephalus przewalskii which inhabit in low altitudes (1400m) at Gansu Jingtai was regarded as a control species, and set P. przewalskii high altitude (HA) acclimation group and P. erythrurus low altitude (LA) acclimation groups. LDH activity and lactate acid content were measured with the method of spectrophotometry, LDH isoenzymes were separated with Native polyacrylamide gel electrophoresis (Native-PAGE), and in additional the full-length cDNA of LDH-A and LDH-B gene which encode the M and H subunit respectively were amplifiacted with the Rapid-amplification of cDNA ends (RACE). In these ways, we expected to explore the LDH adaptation of P. erythrurus to hypoxia and the response of P. przewalskii to HA acclimatization and P. erythrurus to LA acclimatization.The P. erythrurus is considered to be the highest living lizard in the world. Compared with the lowland lizard P. przewalskii, P. erythrurus has a higher LDH activity in heart, and a lower in liver and skeletal muscle. The result of lactate acid concertrationof P. erythrurus is lower than P. przewalskii in heart and no different in other tissues.The LDH isoenzyme analysis result indicated that P. erythrurus has a higher H subunit percentage and H/M ratio than P. przewalskii in heart as well as in skeletal muscle, but not significantly different in liver. The alignment of amino acid sequences of LDH-A showed that P. erythrurus has99%similarity to P. przewalskii. These results indicate that P. erythrurus which living at high altitude do not show higher anaerobic metabolism when compared with the P. przewalskii. On the other hand, the results provide insight that LDH of P. erythrurus underlying the diverse and complex tissue-specific response to hypoxia.After short-term high altitude acclimatization, comparing with the wild group, the P. przewalskii HA group showed a higher LDH activity in20℃and lower lactic acid in heart. However, a lower LDH activity and higher H subunit and H/M ratio were found in liver. These results suggested that high altitude acclimatization does not enhance the ability of anaerobic metabolism in P. przewalskii, which is consistent with the "lactic paradox". Such low level of anaerobic activity can prevent the excessive accumulation of lactic acid in tissue under hypoxia. Compared to the wild group, the P. erythrurus HA acclimated group have a higher LDH activity, H subunit content and H/M ratio in liver, while these is no difference in remaining tissues.These results indicate that the capability of aerobic metabolism in liver may get some enhancements after rich oxygen acclimatation, and elevated LDH activity may be associated with elevated temperature.