THORNTON, S.J.; DANIEL, K.*; HULBERT, A.J.; University of British Columbia, Vancouver, Canada; University of Otago, Dunedin, New Zealand; University of Wollongong, Australia: Seasonal variations in membrane acyl composition and mitochondrial respiratory rate of muscle tissues in European hedgehogs suggest cardiac tissue is preacclimated to hibernation
During hibernation, polyunsaturation of phospholipids increases to maintain membrane fluidity at reduced temperature (homeoviscous adaptation). In European hedgehogs (Erinaceus europaeus), total lipids were obtained from cardiac, gastrocnemius, diaphragm and orbicularis (dermal) muscle by Folch extraction and the phospholipid fraction was evaluated using gas-liquid chromatography. Skeletal muscle from hibernating animals showed an increase in unsaturation index (number of double bonds per 100 acyl chains), percent of unsaturated acyl chains and omega-3 polyunsaturates over summer values. However, cardiac muscle did not show a seasonal change, instead exhibiting high levels of polyunsaturation throughout the year. Mitochondrial respiration of the four muscle types was measured in summer active and winter hibernating animals using a saponin-skinned fibre preparation. Maximal respiration rate (Vmax) of muscle fibre bundles was significantly higher in summer gastrocnemius and diaphragm than from hibernating animals. Cardiac and orbicularis muscle mitochondrial respiration rates were not significantly different between seasons. These data suggest that cardiac muscle tissue maintains a condition suitable for torpid hibernation and does not undergo cyclic changes associated with seasonal metabolic adjustments that characterise a hibernating species.
