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Morita, N1; Iizuka, K1; Okita, K1; Oikawa, T1; Yonezawa, K1; Nagai, T1; Hanada, A1; Sasaki, K1; Tokumitsu, Y1; Murakami, T1; Kitabatake, A1; Kawaguchi, H1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S124
C-15L Free Communication/Poster Cellular/Molecular Physiology of Muscle

1Hokkaido Univ. Grad. Sch. Med., Sapporo, JAPAN, Health Sci. Univ. Hokkaido, Toubetsu, JAPAN

Mammalian cells are exposed to many kinds of stimuli, such as humoral factors, environmental stresses, and mechanical forces. Skeletal muscle contraction gives rise to mechanical forces on the contracting muscles themselves and counter muscles, which are classified into stretch that occurs in the phase of relaxation and intramuscular pressure that is produced in the phase of concentric or isometric contraction. Although it has been reported effects of stretch stress in skeletal muscles, little is known about the effects of pressure stress in skeletal muscles.

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The purpose of this study was to examine the effects of pressure stress on succinate dehydrogenase (SDH) activity in cultured L6 skeletal muscle cell.

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Atmospheric pressure at 160 mmHg without other mechanical stresses was applied to L6 cells using an original apparatus. SDH activity was evaluated by colorimetric assay. The content of lactate and glucose was measured by a lactate analyzer and the mutarotase-glucose oxidase method, respectively.

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SDH activity in pressurized L6 cells was 237.8 ± 5.0% greater compared with that in non-pressurized cells (p < 0.01). The degree of lactate efflux to the medium in non-pressurized cells was 7.7 ± 0.7fÊmol, and that in pressurized cells was decreased to 4.6 ± 0.9fÊmol (p < 0.01). The intracellular lactate level of the pressurized cells was higher than that of the non-pressurized cells (0.32 ± 0.01 vs. 0.23 ± 0.01fÊmol, p < 0.001). Thus, the sum of the lactate efflux and the intracellular lactate contents in the pressurized cells was lower than in the non-pressurized cells. In addition, glucose uptake in pressurized cells seemed greater than in non-pressurized cells.

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These results suggest that pressure stress has enhancing effects on SDH activity and lactate utilization in L6 cells, and that the pressure component in muscle contraction may contribute to activation of aerobic metabolism induced by exercise.

©2003The American College of Sports Medicine