Lack of dystrophin but normal calcium homeostasis in smooth muscle from dystrophic mdx mice

Summary

The free cytosolic Ca²⁺ concentration ([Ca²⁺]_i) in the dystrophin-lacking smooth muscle from mdx mice was studied to gain new insights into the relation between dystrophin and cytoplasmic Ca²⁺ hoemostasis, which was reported to be impaired in the mdx skeletal muscle. We observed that [Ca²⁺]_i, as measured with the fluorescent Ca²⁺ indicator fura-2, was not elevated in resting smooth muscle of the vas deferens from mdx mice, in comparison with control C57 mice. Changes of the external Ca²⁺ concentration evoked similar changes of [Ca²⁺]_i in mdx and control vas deferens. During contraction, cytosolic Ca²⁺ transients were identical, both in amplitude and in kinetics, whether or not dystrophin was present. Stretches evoked similar Ca²⁺ increases in muscles from both strains. Intracellular Ca²⁺ homeostasis appears to be unimpaired in mdx smooth muscle. Thus, the lack of dystrophin per se does not automatically induce a perturbation of Ca metabolism in muscle cells.