Effect of Hypothyroidism on Actin Subdomain-1 Movement Induced by Myosin Subfragment-1 Binding in Fast and Slow Rat Skeletal Muscles

摘要

The orientation and mobility of an N-(iodoacetyl)-(l-naphtyl-5-sulpho-ethylenediamine) fluorescent probe (1.5-IAEDANS) specifically bound to Cys-374 of actin in ghost muscle fibers isolated from fast and slow rat muscles were studied by polarized fluorimetry in the absence and presence of a myosin subfragment-1 (S 1) in intact rats and in animals with a gradual (2-5 weeks) reduction in the level of thyroid hormones (development of hypothyroidism). The binding of SI to F-actin of ghost muscle fibers was shown to induce changes in the orientation of dipoles of the 1.5-IAEDANS fluorescent probe and in the relative amount of the randomly oriented fluorophores that indicates changes in actin subdomain-1 orientation and mobility resulting from formation of its strong binding with SI. This effect is markedly inhibited by the development of hypothyroidism. The maximal effect of hypothyroidism is observed after 34 days of the development of the disease. It is suggested that the change in the thyroid statusin muscle inhibits the ability of F-actin to form strong binding with myosin, which is essential for the generation of force.