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Control of glycolysis in contracting skeletal muscle. II. Turning it off

Gregory J Crowther1, William F Kemper, Michael F Carey

  • 1Department of Physiology and Biophysics, University of Washington Medical Center, Seattle, Washington 98195-7115, USA.

American Journal of Physiology. Endocrinology and Metabolism
|December 12, 2001
PubMed

Insights

Muscle activation controls glycolysis, not substrate availability. After exercise, glycolytic flux rapidly declines despite high substrate levels, indicating direct regulation within the glycolytic pathway itself.

Area of Science:

  • Exercise Physiology
  • Muscle Metabolism
  • Biochemistry

Background:

  • Muscle activation is a key regulator of glycolysis.
  • The precise mechanism of this control remains unclear, with possibilities including calcium-mediated glycogenolysis or direct enzyme modulation.

Purpose of the Study:

  • To distinguish between substrate availability and direct enzymatic control of muscle glycolysis after exercise cessation.
  • To investigate the role of glycogenolysis in supplying substrate (hexose phosphates) to glycolysis post-exercise.

Main Methods:

  • Voluntary 1-Hz exercise was used to elevate hexose phosphate (HP) levels in muscle.
  • Muscle pH, phosphocreatine, and inorganic phosphate (Pi) were measured using 31P magnetic resonance spectroscopy to quantify glycolytic flux, H+, and ATP production.
  • Blood flow occlusion was employed to maintain elevated substrate and metabolite levels after exercise.

Main Results:

  • Glycolytic flux rapidly declined to basal levels within 20 seconds after exercise ceased.
  • Elevated levels of hexose phosphates (HP) and key metabolites (Pi, ADP, AMP) persisted post-exercise due to blood flow occlusion.
  • The decline in glycolytic flux occurred independently of substrate (HP) availability.

Conclusions:

  • Muscle glycolysis is primarily controlled by factors within the glycolytic pathway, not by the rate of glycogen breakdown.
  • The cessation of contractile activity directly mediates the inactivation of glycolysis post-exercise.
  • Glycolysis regulation is independent of glycogenolytic substrate production.

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