Cardiac contractile proteins and sarcoplasmic reticulum in hearts of rats trained by running

Publisher Website
Google Scholar
Abstract
Rats were trained with 2 running protocols previously demonstrated to result in enhanced cardiac performance. Control groups included free-eating sedentary animals and food-restricted animals in which the body weights were the same as the runners. Ca binding by isolated sarcoplasmic reticulum (SR) was slightly but significantly increased in SR from runners at low but not high Ca concentrations at 15 s and 1 min. Ca uptake in the presence of 1 mM oxalate was increased in SR from runners. Actomyosin ATPase activity was increased by 10% (P < 0.001) with one running protocol but not with the other. Myosin Ca2+ ATPase activity and actin-activated ATPase activity were also slightly increased in hearts of runners. In food-restricted cardiac actomyosin ATPase was significantly decreased. Actomyosin ATPase activity was normal in hearts of sedentary animals subjected to water immersion without exercise. Physical training of rats by running, which produces a cardiac mechanical advantage similar to training by swimming, is not accompanied by cardiac biochemical changes of the same magnitude as in the hearts of swimmers.