ATPase activity of actomyosin and myosin in different types of muscles of intact and irradiated animals

Abstract

The large-scale use of sources of ionizing radiation and related accidents caused a fundamentally new problem. The body's resistance to the influence of adverse environmental factors and the probability of pathological disorders are significantly determined by the state of adaptive systems. One of the general manifestations of adaptation is a change in motor activity, which is associated, in particular, with changes in the content of contractile proteins, muscle function, and muscle contraction. It is crucial to understand the detailed mechanisms of muscle tissue functioning in the body of intact animals and animals exposed to different doses of radiation because, in this case, preventive and curative/rehabilitative medical measures should be milder for muscle dysfunctions caused by ionizing radiation The purpose of the work is to investigate the effect of different doses of radiation on Mg²⁺, Ca²⁺-ATPase and K⁺-ATPase activity of actomyosin and myosin in the mechanisms of intact and irradiated in different doses of sexually mature animals in order to find out the mechanisms of adaptation of the organism to the influence of stress factor by studying changes in the activity of Mg²⁺, Ca²⁺-ATPase and K⁺-ATPase in the muscle system. The data obtained showed that irradiation at a dose of 0.5 Gy affects Mg²⁺,Ca²⁺-ATPase and K⁺-ATPase activity, however, these changes occur differently. K⁺-ATPase actomyosin activity in cardiac and skeletal muscles decreased starting from the 1^st day of the experiment. Its gradual increase was observed only on the 30^th day but still, it was smaller when compared with such an indicator in intact animals. It was proved that the Mg²⁺, Ca²⁺-ATPase actomyosin activity in sexually mature animals irradiated at a dose of 1.0 Gy increased 1 day after irradiation in skeletal muscle. In сardiac muscle an acute increase in Mg²⁺, Ca²⁺-ATPase actomyosin activity was observed on the 1^st day and its decrease - by the 30^th day. The conclusion was made that irradiation at a dose of 1.0 Gy is accompanied by skeletal muscle damage, as well as modification of the actomyosin protein complex, which is the major unit of muscle contraction. This leads to changes in its functional activity and is expressed in an increase in K⁺-ATPase actomyosin activity of muscles sensitive to irradiation. We assume such a mechanism of the effect of ionizing radiation on the actomyosin complex. The authors sure that a decrease in Mg²⁺, Ca²⁺-ATP-ase myosin activity as a result of exposure to ionizing radiation at a dose of 1.0 Gy can be caused by a violation of the structure of its active center since the ATPase center of pure myosin is free from interaction with actin, and that is why myosin appears more sensitive to the action of ionizing radiation.