EFFECTS OF Ca{sup}(2+)-BINDING AGENT EGTA ON FIBER CONTRACTILITY AND CONTENT OF SARCOMERIC CYTOSKELETAL PROTEINS OF HINDLIMB SUSPENDED RATS

摘要

The study was purposed to analyze the effects of binding agent (10% EGTA) on soleus fiber contractile characteristics and cytoskeletal sarcomeric proteins in hindlimb suspended rats. Cage control and hindlimb-suspended rats were administered with saline or EGTA i.p. injections. Whereas the fiber diameter of unloaded rat soleus was 17% less than in control group and there were no significant differences between EGTA-treated rats and saline-treated animals. Values of fiber tension in saline-treated unloaded rats were less than in the control group by 45%, and in EGTA-treated rats - by 28%. The Ca/tension curve in hindlimb suspended saline-treated rats shifted to the right, which indicated to the less Ca{sup}(2+) sensitivity of myofibrils of unloaded soleus. At the same time Ca{sup}(2+) sensitivity in EGTA-treated suspended rats even exceeded the control levels. The hindlimb-suspended EGTA-treated rats tended to decrease their titin content to less degree (17%) than group of suspended rats injected with physiological saline (51%). The relative nebulin content decreased significantly (more than 50%) after hindlimb suspension but was not changed in EGTA-treated unloaded rats.