Pagani E D, Solaro R J
Am J Physiol. 1983 Nov;245(5 Pt 1):H713-20. doi: 10.1152/ajpheart.1983.245.5.H713.
We tested whether changes in cardiac myosin ATPase activity induced by swimming exercise in male rats are due to a redistribution of existing isoenzymic forms of ventricular myosin. The isoenzymic profiles were analyzed by nondissociating gel electrophoresis of ventricular samples and compared with ATPase activities of myofibrils prepared from the same ventricle. Myofibrils prepared from hearts of rats in the control sedentary group or from hearts of rats in the groups of 8- or 12-wk swimmers had the same actomyosin Mg2+-ATPase activities measured between pCa 8 and 5. However, the myosin Ca2+-ATPase activity of myofibrils prepared from hearts of 8- or 12-wk swimmers was 20% higher than the activity of control preparations. This increase in activity was in proportion to an increase in the relative amount of V1, the myosin isoenzyme with the highest Ca2+-ATPase activity. Thyroidectomized rats, whose hearts had no detectable V1, were also subjected to the swimming program. In the case of the hypothyroid rats, myofibrillar preparations from controls and 8- or 12-wk swimmers had the same actomyosin Mg2+-ATPase activity, myosin Ca2+-ATPase activity, and the same isoenzyme profiles. Co-electrophoresis of ventricular samples from the euthyroid and hypothyroid controls and swimmers showed no evidence for new variants of myosin. We conclude that the increase in myosin Ca2+-ATPase activity in the ventricles of euthyroid swimmers is due to a redistribution of existing isoforms of myosin and that the redistribution process may require thyroid hormone for its expression.
我们测试了雄性大鼠游泳运动诱导的心肌肌球蛋白ATP酶活性变化是否归因于心室肌球蛋白现有同工酶形式的重新分布。通过对心室样本进行非解离凝胶电泳分析同工酶谱，并与从同一心室制备的肌原纤维的ATP酶活性进行比较。从对照组久坐不动的大鼠心脏或8周或12周游泳组大鼠心脏制备的肌原纤维，在pCa 8至5之间测得的肌动球蛋白Mg2 + -ATP酶活性相同。然而，从8周或12周游泳组大鼠心脏制备的肌原纤维的肌球蛋白Ca2 + -ATP酶活性比对照制剂的活性高20%。这种活性增加与Ca2 + -ATP酶活性最高的肌球蛋白同工酶V1的相对量增加成比例。对心脏中未检测到V1的甲状腺切除大鼠也进行了游泳训练。对于甲状腺功能减退的大鼠，对照组和8周或12周游泳组的肌原纤维制剂具有相同的肌动球蛋白Mg2 + -ATP酶活性、肌球蛋白Ca2 + -ATP酶活性和相同的同工酶谱。对甲状腺功能正常和甲状腺功能减退的对照组及游泳组的心室样本进行共电泳，未发现肌球蛋白新变体的证据。我们得出结论，甲状腺功能正常的游泳者心室中肌球蛋白Ca2 + -ATP酶活性的增加是由于肌球蛋白现有同工型的重新分布，并且这种重新分布过程可能需要甲状腺激素来表达。
