Abstract

VELASCO-RODRIGUEZ, Raymundo; TENE-PEREZ, Carlos Enrique; DEL TORO-EQUIHUA, Mario  and  VASQUEZ, Clemente. Insulin resistance and its effect on excitability and contraction of the skeletal muscle in rats. Rev Cubana Invest Bioméd [online]. 2014, vol.33, n.2, pp. 241-252. ISSN 0864-0300.

Introduction: Insulin resistance is a metabolic condition that affects many tissues including skeletal muscle tissue. The objective of the present study was to analyze whether or not experimentally induced insulin resistance modifies skeletal muscle excitability and contraction in the rat. Methods : Twenty-two healthy Sprague-Dawley rats were used to form two groups. In the experimental group (n=10) insulin resistance was induced by means of oral prednisone administration (45mg/Kg) over a period of 7 days. The control group (n=12) received only water. The following muscle contraction parameters were compared between groups: peak tension, contractile activation, total tension, degree of muscle excitability during threshold curve and response to continuous intravenous insulin infusion. Experiments were carried out in gastrocnemius muscle, utilizing isometric tension registers and electrical stimulation. Variance between groups was analyzed to determine use of Student t test or Mann Whitney U test. Difference between groups was considered statistically significant when P<0.05. Results : (Control group vs Experimental group): 1) Muscle excitability: Rheobase: 0.59± 0.12 V vs 0.27 ± 0.03V (P = 0.19); Chronaxie: 0.07 ms vs 0.08 ms. 2) Muscle contraction parameters: Peak tension: 58.5±5.1 g vs 48.3±4.3 g (P =0.19). Total tension: 0.55±0.13 V/ms vs 0.44±0.05 V/ms ( P=0.45). Contractile activation: 9.13±1.3 ms vs 10.5±1.6 ms (P=0.19). Conclusions: In the results of the present study insulin resistance appears to partially modify muscle fiber excitability in addition to favoring the development of slow, low intensity muscle contractions, suggesting a possible affectation of excitation-contraction coupling in skeletal muscle.

Keywords : insulin resistance; skeletal muscle; muscle contraction; muscle excitability.

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