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Experimental Physiology 93.9 pp 1076-1084
DOI: 10.1113/expphysiol.2008.042440
© The Physiological Society 2008
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Glycolytic activation at the onset of contractions in isolated Xenopus laevis single myofibres

 Brandon Walsh1, Creed M. Stary1, Richard A. Howlett1, Kevin M. Kelley1 and Michael C. Hogan1

1 University of California at San Diego, Department of Medicine, Physiology Division, 9500 Gilman Drive, MC0623A, La Jolla, CA 92093-0623, USA

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 µM; 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 (~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.

(Received 24 February 2008; accepted after revision 23 May 2008; first published online 30 May 2008)
Corresponding author M. C. Hogan: University of California at San Diego, Department of Medicine, Physiology Division, 9500 Gilman Drive, MC0623A, La Jolla, CA 92093-0623, USA.  Email: mchogan{at}ucsd.edu






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