Effects of volatile anesthetics on crossbridge mechanism of skeletal muscle--effects on the crossbridge in contraction
Nishiwaki, T.; Miyagishima, T.; Oka, N.
Masui. Japanese Journal of Anesthesiology 40(11): 1666-1673
1991
ISSN/ISBN: 0021-4892 PMID: 1766118 Document Number: 384207
The suppressive effect of enflurane on the maximal activated force in skinned muscle fiber at high Ca2+ concentration was determined in our previous report. This result suggests that the acto-myosin system might be inhibited in the presence of enflurane. Therefore, the present study was performed to identify the sites and to clarify the mechanism of the above mentioned action. For this purpose, the stiffness during Ca2+ contraction was measured using mechanically-skinned frog muscle fiber. The force oscillation was given by high frequently sinusoidal length perturbation. The maximum shortening speed, which is considered to be a parameter of crossbridge kinetics, was also measured using the slack method on frog and rat muscle fibers. The results of this study are summarized as follows: 1. The total force was decreased when enflurane or halothane was present, while the stiffness, which is a parameter of the number of attachments (crossbridges), was decreased only by enflurane. Furthermore, the stiffness over force ratio, which is a parameter of the individual force generated by each crossbridge, was increased when enflurane or halothane was present. These results initially seem contradictory. However, the contradiction seems far smaller in light of our assumption that the amplitude of reduction of the force generated by each crossbridge was much higher in the presence of halothane than in the presence of enflurane. 2. The maximum shortening speed was also decreased when enflurane or halothane was present. Therefore, it was suggested that enflurane and halothane have a potentiality to decrease the rate of crossbridge cycling.