Influence of tension time on muscle fiber sarcolemmal injury in rat diaphragm
Journal of applied physiology
Influence of tension time on muscle fiber sarcolemmal injury in rat diaphragm. J. Appl. Physiol. 88: 135-141, 2000.-We hypothesized that the amount of sarcolemmal injury is directly related to the total tension time (TT tot ), calculated as mean tension ϫ total stimulation time. Diaphragm strips from Sprague-Dawley rats were superfused at optimal muscle length with Krebs containing procion orange to identify sarcolemmal injury. TT tot was induced by stimulation with 100 Hz for 3 min at duty
... r 3 min at duty cycles of 0.02, 0.15, 0.3, and 0.6, or with continuous contractions at 0.2, 0.4, 0.6, and 1.0 of maximal tension. A significant positive correlation between TT tot and the percentage of fibers with injured sarcolemma (r 2 ϭ 0.63, P Ͻ 0.05) is seen. Stimulation (at 100 Hz, duty cycle ϭ 1) resulted in fast fatigue with low injury, likely caused by altered membrane conductivity. Stimulations inducing the largest injury are those showing progressive force loss and high TT tot , where injury may be due to activation of membrane degradative enzymes. The maximal tension measured at 20 min poststimulation was inversely related to the number of fibers injured, suggesting loss of force is caused by cellular injury. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.