Possible Mechanisms for the Effect of Protein Sensitization on Contractile Function of Fast and Slow Muscles in Mice

Abstract

We studied the mechanisms underlying the effect of immunobiological reorganization of the organism on contractile function of isolated skeletal muscles from mouse leg (fast muscle, m. extensor digitorum longus; and slow muscle, m. soleus). Protein sensitization was accompanied by changes in contractile properties of fast and slow skeletal muscles. These changes were differently directed in muscles with various phenotypes. The force of carbachol-induced contraction (cholinergic agonist) increased in the slow muscle, but decreased in the fast muscle. The direction of changes in the force of carbachol-induced contractions under conditions of protein sensitization in skeletal muscles correlates with changes in non-quantal secretion of acetylcholine in the endplate (H-effect). Opposite changes in functional properties of fast and slow muscles from mouse leg during protein sensitization are related to choline-mediated excitation of the muscle fiber membrane. Our results suggest that changes in contractile function of skeletal muscles during protein sensitization are associated with variations in choline-mediated excitation of the muscle fiber membrane and modification of electromechanical coupling.