Glycolytic regulation during an aerobic rest-to-work transition in dog gracilis muscle.
Glycogen phosphorylase activity and several glycolytic intermediates were measured at rest and after 5, 10, 15, 30, 60, and 180 s of twitch stimulation at 4 Hz in fast-frozen samples of gracilis muscle. During an initial burst of glycolysis (0-5 s) only 3-phosphoglycerate and lactate accumulate. These changes are reversed during the period of low glycolytic flux (5-30 s). During a second burst of glycolysis (30-60 s) most glycolytic intermediates increase. The levels of glycogen phosphorylase a changes in parallel with the initial burst of glycolysis but remain at resting levels throughout the second burst. The phosphoglycerate mutase-enolase steps deviate from equilibrium during the initial burst of glycolysis, suggesting a transiently rate-limiting role. Analysis using a model of phosphofructokinase kinetics indicates that combined changes in cytosolic pH (R. J. Connett, J. Appl. Physiol. 63: 2360-2365, 1987) and free [ADP] and [AMP] can account for the initial burst of glycolysis. The second burst of glycolysis requires other regulatory factors. It is concluded that an initial alkalization is a major regulatory factor in the early burst of glycolysis during a rest-to-work transition in red muscle.
Connett
R J
RJ
Department of Physiology, School of Medicine and Dentistry, University of Rochester, New York 14642.
D000818:Animals; D002951:Citrates / Q000378:metabolism; D019343:Citric Acid; D004285:Dogs; D004558:Electric Stimulation; D005121:Extremities; D005988:Glyceric Acids / Q000378:metabolism; D006019:Glycolysis; D007773:Lactates / Q000097:blood; D009132:Muscles / Q000201:enzymology* / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010477:Perfusion; D010736:Phosphoglycerate Mutase / Q000378:metabolism; D010762:Phosphorylase a / Q000378:metabolism; D005082:Physical Exertion; D013997:Time Factors
D002951:Citrates; D005988:Glyceric Acids; D007773:Lactates; D019343:Citric Acid; C005156:3-phosphoglycerate; D010762:Phosphorylase a; D010736:Phosphoglycerate Mutase; D010100:Oxygen