Abstract:
The Red-eared slider (Trachemys scripta) is remarkably tolerant to the anoxic conditions of hibernation. During the winter. these turtles hibernate under a thin layer of mud where the temperature is approximately 5 °C and the oxygen availability is close to zero. During hibernation, the turtles are dependent upon anaerobic glycolysis as the primary source of energy generation. As lactate dehydrogenase (LDH) is a key enzyme of the anaerobic pathway, the possible molecular adaptations of LDH in hibernating turtles were investigated in this study. Ten turtles were placed into simulated hibernation at 5 °C for five 1110nths. Control animals were placed in similar conditions at room temperature. Since LDH can exists in the forms of five isozymes, we analyzed LDH isolated from the turtle heart skeletal muscle, and liver by electrophoresis, followed by densitometric analysis. The densitometry was performed to determine if differences in the percentage of the LDH isozymes in these tissues occurred between hibernating and room temperature turtles. The activity ofLDH was also determined at 5 °C and 30°C for each of the above tissues in both groups of turtles. No statistical differences were found in the mean percentage of LDH isozymes when comparing similar tissues between hibernating and room temperature turtles. However. hibernating turtles had higher LDH activities in all tissues tested as compared to the room temperature turtles. At 5 °C the mean LDH activity of the hibernating turtle skeletal muscle was 3.5 times greater, heart and liver were 1.75 times greater than that oflike tissues in room temperature turtles, while at 30°C the mean LDH activity in skeletal muscle was 2.0 and liver 1.5 times greater in hibernating turtles, respectively. Thus, it appears that the LDH activity of hibernating turtles, particularly within skeletal muscle, does adapt during hibernation, a feature which contributes to their survival during these prolonged and extreme periods.
