ORTIZ, S*; HAMMOND, K. A.; CARDULLO, R. A. ; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside: The effects of high altitude on skeletal muscle enzyme capacity in deer mice, Peromyscus maniculatus

An organism�s developmental environment ultimately determines the physiological framework in which it is able to operate most efficiently. Organisms that develop at high altitude face many challenges, such as acquiring oxygen needed for proper growth and development, so they often make physiological adjustments (larger lungs and higher hematocrit levels) to cope with low oxygen availability. Specifically, the specific activity of enzymes involved in anabolism and catabolism are often altered to meet greater physiological demands. We examined enzyme activities of phosphofructokinase (PFK), lactate dehydrogenase (LDH) (glycolytic enzymes) and citrate synthase (CS) (oxidative enzyme) in the skeletal muscle of deer mice, Peromyscus maniculatus, born at and/or acclimated to high (3800m) and low (380m) altitudes. Mice were placed into one of four treatment groups: high born/low acclimated, high born/high acclimated, low born/ high acclimated and low born/low acclimated and half of the mice in each group were acclimated to either warm (25�) or cold (8�) temperatures. Although no significant effects of birth or acclimation site were associated with the mass specific activities of either PFK or CS, the high born/high acclimated group had significantly greater leg mass than low born/low acclimated mice (p = 0.0384). As a result, whole muscle CS and LDH activities increased by 25% and 29%, respectively, in high altitude born mice, indicating the need for greater enzymatic capacity as a means of coping with low oxygen partial pressures at high altitude.