Effects of hypothermia on energy metabolism in rat and Richardson's ground squirrel hearts

Darrell D. Belke 1 , Lawrence C. H. Wang 2 , and Gary D. Lopaschuk 1 1 Departments of Pharmacology and Pediatrics and 2 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2S2 Received 7 August 1996; accepted in final form 22 November 1996. Belke, Darrell D., Lawrence C. H. Wang, and Gary D. Lopaschuk. Effects of hypothermia on energy metabolism in rat and Richardson's ground squirrel hearts. J. Appl. Physiol. 82(4): 1210-1218, 1997. Glycolysis, glucose oxidation, palmitate oxidation, and cardiac function were measured in isolated working hearts from ground squirrels and rats subjected to a hypothermia-rewarming protocol. Hearts were perfused initially for 30 min at 37°C, followed by 2 h of hypothermic perfusion at 15°C, after which hearts were rewarmed to 37°C and further perfused for 30 min. Functional recovery in ground squirrel hearts was greater than in rat hearts after rewarming. Hypothermia-rewarming had a similar general effect on the various metabolic pathways in both species. Despite these similarities, total energy substrate metabolic rates were greater in rat than ground squirrel hearts during hypothermia despite a lower level of work being performed by the rat hearts, indicating that rat hearts are less efficient than ground squirrel hearts during hypothermia. After rewarming, energy substrate metabolism recovered completely in both species, although cardiac work remained depressed in rat hearts. The difference in functional recovery between rat and ground squirrel hearts after rewarming cannot be explained by general differences in energy substrate metabolism during hypothermia or after rewarming. glucose oxidation; glycolysis; fatty acid oxidation; cardiac efficiency 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society