SARKAR, S; KINSEY, ST; MCCALL, RD; University of North Carolina at Wilmington; University of North Carolina at Wilmington; University of North Carolina at Wilmington: Lactate production in mice with an inherited capacity for hypoxic exercise.

The present study examined the effects of acclimation to hypobaric hypoxia on lactate production in mice with inherited differences in hypoxic exercise tolerance. Previous work has demonstrated that two genes of major effect are principally responsible for large differences in hypoxic exercise tolerance in mice. The three strains of mice BALB/cBy (C) and C57BL/6J (B6) and their F1 hybrid had similar capacities for hypoxic exercise following exposure to normoxia. Following eight weeks of exposure to hypobaric hypoxia (1/2 atm),the C mice had little improvement in hypoxic exercise performance, B6 mice improved considerably while the F1 hybrids had an endurance capacity that far exceeded either of the two parental strains. Lactate concentrations at rest, during hypoxic exercise (2,10 and 20 min) and at fatigue were determined in the right ventricle of heart, gastrocnemius muscle and blood. All mice had decreased lactate accumulation after hypoxic exposure and the best performing F1 mice had the lowest lactate levels during exercise. We conclude that lower lactate production in the F1 mice indicates that oxygen delivery to skeletal and heart muscle is enhanced in F1 mice.