Apparent Elevation of α-Bungarotoxin Binding Attendant upon Maturational Defect of Forelimb Muscle in Muscular Dystrophic Mice

Abstract

Postnatal developmental changes in forelimb muscle (m. triceps brachii) were studied in dystrophic mice (C57BL/6J dy/dy). At an early age of 2.3 weeks, tissue weight and α-bungarotoxin uptake per unit weight of the muscle were not different between normal and dystrophic mice. With age, the muscle weight increased markedly in normal mice against only a slight increase in dystrophic ones, and the toxin uptake decreased in normal but not almost at all in dystrophic mice. Significant differences between normal and dystrophic mice were observed after 4 and 6 weeks of age as to toxin uptake and muscle weight, respectively. The muscle-body weight ratio was very similar in normal and dystrophic mice and it varied little during the period from 2.3 to 8 weeks of age. Diameter-frequency analysis showed that muscle fibers were much thinner in dystrophic than in nor-mal mice at 12 weeks old. The present findings strongly suggest that in dystrophic mice muscle fibers suffer from a maturational defect in the forelimbs as well.