Effect of exercise on the skeletal myosin of growing rat.

In order to study the effect of running on ATPase activity of myofibril and myosin in the hindlimb muscles, male wister rats of the same venter weighing approximately 50 g were housed in individual cages and allowed to run unimpeded on a treadwheel for 25-30 days. The myofibril and myosin prepared from the exercised rats had lower activation energy of ATP hydrolysis reaction and higher specific ATPase activity than those from the control rats. The myosin prepared from the running-group contained a much higher amount of the light chain having a molecular weight of 16,000, characteristic of white skeletal myosin, than that from the control group. These observations suggest that physical training changed the ratio of populations in myosin molecules, for instance, white and red skeletal myosin.