Mechanically skinned, single muscle fibers, isometrically activated in pH and Ca2+ (Sr2+) buffered solutions were used to examine the function of the contractile apparatus in slow- and fast-twitch fibers from soleus (SOL, predominantly slow-twitch) and extensor digitorum longus (EDL, predominantly fast-twitch) muscles of streptozotocin (STZ)-induced diabetic rats and age-matched controls. Three and 14 days after STZ administration, the contractile properties of muscle fibers from diabetic rats did not differ significantly from those of controls with respect to several mechanical parameters, such as maximum Ca-activated tension, activation threshold, and sensitivity to Ca2+ and Sr2+. In contrast, 28 days after STZ administration, 37.5% of the fast-twitch EDL fibers developed maximum activated tensions (77.1 ± 10.4 kN/m2), which were significantly lower than those developed by controls (244.0 ± 14.3 kN/m2), and the slow-twitch SOL fibers displayed a significantly higher sensitivity to Ca2+ (and Sr2+) than the controls. All fibers from diabetic rats, including the low-tension EDL fibers and higher Ca sensitivity SOL fibers displayed control-like electrophoretic profiles of the major myofibrillar proteins. Taken together with data from earlier studies on the effects of long-term diabetes on whole skeletal muscle contractility, these results strongly suggest that 1) the decrease in tetanic tension output of EDL muscles induced by diabetes is caused mainly by direct effects of the diabetic condition on the contractile/regulatory system of a subpopulation of fast-twitch fibers, which develop little force, and 2) the diabetes-induced slowing of twitch times of SOL muscles is caused in part by the increased sensitivity to Ca2+ of the contractile apparatus in the slow-twitch fibers.
Original Articles|
May 01 1994
Single-Fiber Study of Contractile and Biochemical Properties of Skeletal Muscles in Streptozotocin-Induced Diabetic Rats
Gabriela M M Stephenson;
Gabriela M M Stephenson
Department of Zoology, La Trobe University
Bundoora, Victoria, Australia
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Alexia O'Callaghan;
Alexia O'Callaghan
Department of Zoology, La Trobe University
Bundoora, Victoria, Australia
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D George Stephenson
D George Stephenson
Department of Zoology, La Trobe University
Bundoora, Victoria, Australia
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Address correspondence to Dr. Gabriela M. M. Stephenson, Department of Zoology, La Trobe University, Bundoora, Victoria 3083 Australia.
Diabetes 1994;43(5):622–628
Article history
Received:
August 27 1993
Revision Received:
November 17 1993
Accepted:
November 17 1993
PubMed:
8168636
Citation
Gabriela M M Stephenson, Alexia O'Callaghan, D George Stephenson; Single-Fiber Study of Contractile and Biochemical Properties of Skeletal Muscles in Streptozotocin-Induced Diabetic Rats. Diabetes 1 May 1994; 43 (5): 622–628. https://doi.org/10.2337/diab.43.5.622
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