Sb
III. Effects of Chronic Hypoxia on Muscle Enzyme Act ivities* H. Howaldt , D. Pett e2 , J.-A. Simoneau2 , A. Ube?, H. Hoppele? , and P. Cerretelli4 'Institute of the Swiss School for Physical Education and Sports, Magglingen, Switzerland
Abstract H. Howald, D. Pette, J.-A. Simoneau,A. Uber, H. Hoppeler, and?. Cerreteii, Effects of Chronic Hypoxia on Muscle Enzyme Activities. mt J Sports Med, Vol 11, Suppi l,ppSlO—S14, 1990. Biopsies from the vastus lateralis muscle of
seven
participants in the Swiss expedition to Mt. Everest
and Lhotse in 1986 were taken before departure to and after
return from high altitude, and used for measurements of maximal activities of 12 reference enzymes of anaerobic and aerobic-oxidative metabolic pathways. The results indicated that strenuous exercise at high altitude induced increases in enzyme activities of glycolysis and decreases in enzyme activities of terminal substrate oxidation (the citric acid cycle, fatty acid oxidation, ketone body utilization, respiratory chain). The decreases in enzyme activities of aero-
bic-oxidative metabolism were related to similar decrements in mitochondrial volume density, which suggests that the enzymic changes resulted from a loss of mitochondrial structure rather than from qualitative changes of the mitochondrial population. These changes indicated that strenuous exercise may intensify the stress of high-alti-
tude exposure and, thus, induce an aerobic to anaerobic shift of muscle energy metabolism.
sity of total mitochondria, representing approximately 5% of the muscle fiber volume, was even more severely depressed, i. e., by almost 30%. This finding raises the question as to whether the decrease in mitochondrial volume density simply reflects a quantitative diminution of mitochondrial mass or whether there are concomitant qualitative changes in some mitochondrial characteristics. To evaluate the functional properties of mitochondria, we measured activities of key enzymes of several mitochondrial functions such as the citric acid cycle, fatty acid oxidation, ketone body utilization, and the respiratory chain. In addition, we were also interested in gaining insight into changes of glycolytic enzyme activities and of other cytosolic enzymes related to energy metabolism. Materials and Methods
Subjects and Muscle Samples Seven male subjects participating in a Swiss expedition to Mt. Everest and Lhotse in 1986 gave their informed consent for having muscle biopsies taken before departure to and after return from high altitude. Details of expedition characteristics, acclimatization profiles, etc. are given by Cerretelli et al. (6). Briefly, the subjects stayed 6 weeks at the base camp,
located at 5300 m, with occasional exposures to altitudes in excess of 8000 m. Age, body mass, thigh muscle mass, and VO2max of the seven subjects before and after altitude exposure are shown in Table I.
Biopsies of m. vastus lateralis were taken at
Key words
aerobic-oxidative metabolism, enzyme activities, glycolysis, high altitude, hypoxia, mitochondria, skeletal muscle
mid-thigh level using the Bergstrom needle (2). The major part of the tissue was processed for electron microscopy. Results of Table 1 Physical and physiologic characteristics of subjects (means SD, n = 7). * = p
III. Effects of Chronic Hypoxia on Muscle Enzyme Act ivities* H. Howaldt , D. Pett e2 , J.-A. Simoneau2 , A. Ube?, H. Hoppele? , and P. Cerretelli4 'Institute of the Swiss School for Physical Education and Sports, Magglingen, Switzerland
Abstract H. Howald, D. Pette, J.-A. Simoneau,A. Uber, H. Hoppeler, and?. Cerreteii, Effects of Chronic Hypoxia on Muscle Enzyme Activities. mt J Sports Med, Vol 11, Suppi l,ppSlO—S14, 1990. Biopsies from the vastus lateralis muscle of
seven
participants in the Swiss expedition to Mt. Everest
and Lhotse in 1986 were taken before departure to and after
return from high altitude, and used for measurements of maximal activities of 12 reference enzymes of anaerobic and aerobic-oxidative metabolic pathways. The results indicated that strenuous exercise at high altitude induced increases in enzyme activities of glycolysis and decreases in enzyme activities of terminal substrate oxidation (the citric acid cycle, fatty acid oxidation, ketone body utilization, respiratory chain). The decreases in enzyme activities of aero-
bic-oxidative metabolism were related to similar decrements in mitochondrial volume density, which suggests that the enzymic changes resulted from a loss of mitochondrial structure rather than from qualitative changes of the mitochondrial population. These changes indicated that strenuous exercise may intensify the stress of high-alti-
tude exposure and, thus, induce an aerobic to anaerobic shift of muscle energy metabolism.
sity of total mitochondria, representing approximately 5% of the muscle fiber volume, was even more severely depressed, i. e., by almost 30%. This finding raises the question as to whether the decrease in mitochondrial volume density simply reflects a quantitative diminution of mitochondrial mass or whether there are concomitant qualitative changes in some mitochondrial characteristics. To evaluate the functional properties of mitochondria, we measured activities of key enzymes of several mitochondrial functions such as the citric acid cycle, fatty acid oxidation, ketone body utilization, and the respiratory chain. In addition, we were also interested in gaining insight into changes of glycolytic enzyme activities and of other cytosolic enzymes related to energy metabolism. Materials and Methods
Subjects and Muscle Samples Seven male subjects participating in a Swiss expedition to Mt. Everest and Lhotse in 1986 gave their informed consent for having muscle biopsies taken before departure to and after return from high altitude. Details of expedition characteristics, acclimatization profiles, etc. are given by Cerretelli et al. (6). Briefly, the subjects stayed 6 weeks at the base camp,
located at 5300 m, with occasional exposures to altitudes in excess of 8000 m. Age, body mass, thigh muscle mass, and VO2max of the seven subjects before and after altitude exposure are shown in Table I.
Biopsies of m. vastus lateralis were taken at
Key words
aerobic-oxidative metabolism, enzyme activities, glycolysis, high altitude, hypoxia, mitochondria, skeletal muscle
mid-thigh level using the Bergstrom needle (2). The major part of the tissue was processed for electron microscopy. Results of Table 1 Physical and physiologic characteristics of subjects (means SD, n = 7). * = p
