Glycolytic activation at the onset of contractions in isolated Xenopus laevis single myofibres.

Abstract

Intracellular pH (pHi) was measured in isolated Xenopus laevis single myofibres at the onset of contractions, with and without glycolytic blockade, to investigate the time course of glycolytic activation. Single myofibres (n=8; CON) were incubated in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoyxmethyl ester (10 microM; for fluorescence measurement of pHi) and stimulated for 15 s at 0.67 Hz in anoxia in the absence (control condition; CON) and presence of a glycolytic inhibitor (1 mM iodoacetic acid; IAA). Intracellular pHi and tension were continuously recorded, and the differences in pHi between conditions were used to estimate the activation time of glycolysis. An immediate and steady increase in pHi (initial alkalosis) at the onset of contractions was similar between CON and IAA trials for the first 9 s of the contractile bout. However, from six contractions (approximately 10 s) throughout the remainder of the bout, IAA demonstrated a continued rise in pHi, in contrast to a progressive decrease in pHi in CON (P<0.05). These results demonstrate, with high temporal resolution, that glycolysis is activated within six contractions (10 s at 0.67 Hz) in single Xenopus skeletal muscle fibres.

• Authors: Brandon Walsh, Creed M Stary, Richard A Howlett, Kevin M Kelley, Michael C Hogan
• Journal: Experimental physiology (Exp Physiol) Vol. 93 Issue 9 Pg. 1076-84 (Sep 2008) ISSN: 0958-0670 [Print] England
• PMID: 18515473 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Enzyme Inhibitors
• Fluoresceins
• Fluorescent Dyes
• Phosphocreatine
• 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein
• Iodoacetic Acid

Topics

• Animals
• Enzyme Inhibitors (pharmacology)
• Female
• Fluoresceins
• Fluorescent Dyes
• Glycolysis (drug effects, physiology)
• Hydrogen-Ion Concentration
• Iodoacetic Acid (pharmacology)
• Muscle Contraction (physiology)
• Myofibrils (physiology)
• Phosphocreatine (metabolism)
• Time Factors
• Xenopus laevis