AJP - Endocrinology and Metabolism, Vol 239, Issue 6 454-E460, Copyright © 1980 by American Physiological Society

ARTICLES

Epitrochlearis muscle. I. Mechanical performance, energetics, and fiber composition

R. Nesher, I. E. Karl, K. E. Kaiser and D. M. Kipnis

An in vitro rat muscle preparation is described that can contract at rates of 12-240 twitches/min. Maximum dF/dt paralleled maximum twitch tension, their ratio being constant at approximately 8 ms for contraction rates of 12-120 twitches/min. Time to peak tension was 8-13 ms, time to peak dF/dt 5-8 ms, and half-relaxation time 4 ms. These parameters were unaffected by rate of contraction or duration of isometric work. Differential ATPase staining demonstrated that 60-65% of the fibers were fast-twitch white, 20% fast-twitch red, and 15% slow-twitch red. The preponderance of fast-twitch fibers correlated with the observed mechanical performance of the muscle. Muscles contracting for 60 min at rates up to 48 twitches/min maintained total adenine nucleotide content (ATP, ADP, AMP) at near resting levels. At higher twitch rates (72-240 twitches/min), total adenine nucleotide content decreased 40%, reflecting exclusively a fall in ATP in the presence of adequate phosphocreatine stores. Adequate oxygenation was reflected by lactate-to-pyruvate ratios in the range of 11-15 at all rates of contraction.

This article has been cited by other articles:

				A. A. Gupte, G. L. Bomhoff, and P. C. Geiger Age-related differences in skeletal muscle insulin signaling: the role of stress kinases and heat shock proteins J Appl Physiol, September 1, 2008; 105(3): 839 - 848. [Abstract] [Full Text] [PDF]

				L. Miyamoto, T. Toyoda, T. Hayashi, S. Yonemitsu, M. Nakano, S. Tanaka, K. Ebihara, H. Masuzaki, K. Hosoda, Y. Ogawa, et al. Effect of acute activation of 5'-AMP-activated protein kinase on glycogen regulation in isolated rat skeletal muscle J Appl Physiol, March 1, 2007; 102(3): 1007 - 1013. [Abstract] [Full Text] [PDF]

				S. Terada and I. Tabata Effects of acute bouts of running and swimming exercise on PGC-1{alpha} protein expression in rat epitrochlearis and soleus muscle Am J Physiol Endocrinol Metab, February 1, 2004; 286(2): E208 - E216. [Abstract] [Full Text] [PDF]

				S. Terada, I. Muraoka, and I. Tabata Changes in [Ca2+]i induced by several glucose transport-enhancing stimuli in rat epitrochlearis muscle J Appl Physiol, May 1, 2003; 94(5): 1813 - 1820. [Abstract] [Full Text] [PDF]

				E. J. Henriksen, T. R. Kinnick, M. K. Teachey, M. P. O'Keefe, D. Ring, K. W. Johnson, and S. D. Harrison Modulation of muscle insulin resistance by selective inhibition of GSK-3 in Zucker diabetic fatty rats Am J Physiol Endocrinol Metab, May 1, 2003; 284(5): E892 - E900. [Abstract] [Full Text] [PDF]

				N. Jessen, R. Pold, E. S. Buhl, L. S. Jensen, O. Schmitz, and S. Lund Effects of AICAR and exercise on insulin-stimulated glucose uptake, signaling, and GLUT-4 content in rat muscles J Appl Physiol, April 1, 2003; 94(4): 1373 - 1379. [Abstract] [Full Text] [PDF]

				C. S. Choi, Y.-B. Kim, F. N. Lee, J. M. Zabolotny, B. B. Kahn, and J. H. Youn Lactate induces insulin resistance in skeletal muscle by suppressing glycolysis and impairing insulin signaling Am J Physiol Endocrinol Metab, August 1, 2002; 283(2): E233 - E240. [Abstract] [Full Text] [PDF]

				R. Aslesen, E. M. L. Engebretsen, J. Franch, and J. Jensen Glucose uptake and metabolic stress in rat muscles stimulated electrically with different protocols J Appl Physiol, September 1, 2001; 91(3): 1237 - 1244. [Abstract] [Full Text] [PDF]

				R. Bergeron, R. R. Russell III, L. H. Young, J.-M. Ren, M. Marcucci, A. Lee, and G. I. Shulman Effect of AMPK activation on muscle glucose metabolism in conscious rats Am J Physiol Endocrinol Metab, May 1, 1999; 276(5): E938 - E944. [Abstract] [Full Text] [PDF]

				H. H. Host, P. A. Hansen, L. A. Nolte, M. M. Chen, and J. O. Holloszy Glycogen supercompensation masks the effect of a traininginduced increase in GLUT-4 on muscle glucose transport J Appl Physiol, July 1, 1998; 85(1): 133 - 138. [Abstract] [Full Text] [PDF]