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GLUCOSE 6-PHOSPHATE ALTERS RAT SKELETAL MUSCLE CONTRACTILE APPARATUS AND SARCOPLASMIC RETICULUM FUNCTION

Published online by Cambridge University Press:  03 January 2001

JAY H. WILLIAMS ,
CHRISTOPHER W. WARD ,
ESPEN E. SPANGENBURG ,
REAGAN NELSON ,
STASINOS STAVRIANEAS  and
GARY A. KLUG
JAY H. WILLIAMS
Affiliation:
Muscular Function Laboratory. Department of Human Nutrition, Foods and Exercise Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
CHRISTOPHER W. WARD
Affiliation:
Muscular Function Laboratory. Department of Human Nutrition, Foods and Exercise Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
ESPEN E. SPANGENBURG
Affiliation:
Muscular Function Laboratory. Department of Human Nutrition, Foods and Exercise Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
REAGAN NELSON
Affiliation:
Muscular Function Laboratory. Department of Human Nutrition, Foods and Exercise Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
STASINOS STAVRIANEAS
Affiliation:
Muscular Function Laboratory. Department of Human Nutrition, Foods and Exercise Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
GARY A. KLUG
Affiliation:
Department of Exercise and Movement Studies University of Oregon, Eugene, OR 97403, USA
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Abstract

We investigated the effects of glucose 6-phosphate (G6P) on skeletal muscle contractile apparatus and sarcoplasmic reticulum (SR) function. Using rat extensor digitorum longus fibres, the presence of 5 mM G6P decreased the Ca2+ sensitivity of both force production and actomyosin ATPase (AM-ATPase) activity. Conversely, maximal Ca2+-activated force was unaffected while maximal AM-ATPase activity was increased by 37 %. In SR vesicles isolated from rat gastrocnemius, G6P markedly altered Ca2+ handling. It increased Ca2+-stimulated Ca2+-ATPase activity but depressed the net rate of Ca2+ uptake. This latter effect appears to be due to G6P-stimulated Ca2+ release. When G6P was added to Ca2+-loaded vesicles, a small, transient release of Ca2+ was elicited. In addition, G6P lowered the threshold for Ca2+-induced Ca2+ release but depressed the net rates of both AgNO3- and caffeine-induced releases. It is possible that the accumulation of G6P during muscular activity may adversely affect muscle force production and contribute to the fatigue process via its action on the contractile apparatus and SR.

Type
Research Article
Information
Experimental Physiology , Volume 83 , Issue 4 , July 1998 , pp. 489 - 501
Copyright
© The Physiological Society 1998

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