The role of changes in citrate synthase and lactate dehydrogenase tissue activities in the thermal acclimation response of a winter-dormant fish, the cunner (Tautogolabrus adspersus)

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University of New Brunswick
The mechanisms underlying the winter dormancy seen in many fishes living at temperate to high latitudes has not been fully explored. Winter-active fishes enhance tissue enzyme activities at low temperatures in winter to help maintain whole-animal performance capacity, which would otherwise be lower in the cold. Cunner (Tautogolabrus adspersus), despite being a winter-dormant model species, in recent laboratory experiments also have shown enhanced whole-animal exercise performance in the cold, but nothing is known about the underlying mechanisms of this compensation. I hypothesized that increases in citrate synthase (CS) and lactate dehydrogenase (LDH) enzyme activities in tissues may help explain the compensation of exercise performance, which depends upon flux through these metabolic enzymes. In a previous experiment, juvenile cunner were acclimated to a range of temperatures and exhaustive swimming performance was measured. I measured activities of CS and LDH in white muscle and liver from these cunner acclimated to 2, 8, and 14°C, which bracket the temperature at which cunner become dormant (7.2°C). At 2°C, liver showed significant increases in LDH activity while CS activity was decreased. In white muscle, neither CS or LDH enzymes were significantly different across acclimation temperatures. I concluded that enhancement of metabolic enzyme activities in white muscle or liver of a winter-dormant model species is not an important determinant of the compensation of whole-animal exercise performance at colder temperatures.