Dillmann W H
Endocrinology. 1985 Jun;116(6):2160-6. doi: 10.1210/endo-116-6-2160.
Studies were conducted to determine if the level of cardiac Ca+2-activated myosin ATPase activity and ventricular myosin isoenzyme distribution are influenced by both T3 administration and fructose feeding. Previous studies have shown that in the cardiac ventricle of hypothyroid rats, only myosin V3 is present, and the Ca+2-activated myosin ATPase activity is markedly decreased. Hypothyroid [thyroidectomized (Tx)] rats were fed a diet containing 60% fructose or a regular diet (47% complex carbohydrates) for 4 weeks. Fructose feeding of hypothyroid rats led to a significant increase in Ca+2-activated myosin ATPase activity (Tx regular diet, 0.33 +/- 0.02 mumol Pi/mg protein X min; Tx fructose diet, 0.54 +/- 0.04 mumol Pi/mg protein X min). In addition, myosin V1 was detectable in the heart of fructose-fed Tx rats, but was absent in Tx rats on the regular diet. To determine if fructose had an effect of similar magnitude in animals of different thyroid states, Tx rats were injected with 0.075, 0.150, 0.225, and 0.300 micrograms T3/100 g BW daily and placed on fructose or regular diets. The fructose-induced increase in Ca+2-myosin ATPase activity was between 24-27% in Tx rats receiving 0-0.15 micrograms T3/100 g BW daily. In animals receiving 0.225 and 0.300 micrograms T3/100 g BW daily, fructose feeding did not induce a significant increase in myosin ATPase activity. This is due to the fact that the Ca+2-activated myosin ATPase activities of euthyroid and hyperthyroid animals are not significantly different from each other. In hypothyroid rats receiving a 60% glucose diet, Ca+2-myosin ATPase activity showed a significant 20% increase above the value in regular diet-fed Tx rats. Fructose- and glucose-induced changes in Ca+2-myosin ATPase activity occurred in the absence of changes in thyroid hormone or insulin levels. Our findings may indicate that cardiac carbohydrate consumption influences the predominance of ventricular myosin isoenzymes in the rat heart.
开展了多项研究以确定甲状腺素（T3）给药和果糖喂养是否会影响心脏中钙离子激活的肌球蛋白ATP酶活性水平以及心室肌球蛋白同工酶分布。先前的研究表明，在甲状腺功能减退大鼠的心室中，仅存在肌球蛋白V3，且钙离子激活的肌球蛋白ATP酶活性显著降低。对甲状腺功能减退[甲状腺切除（Tx）]的大鼠喂食含60%果糖的饮食或常规饮食（47%复合碳水化合物），持续4周。对甲状腺功能减退大鼠喂食果糖导致钙离子激活的肌球蛋白ATP酶活性显著增加（Tx常规饮食组，0.33±0.02微摩尔无机磷/毫克蛋白质×分钟；Tx果糖饮食组，0.54±0.04微摩尔无机磷/毫克蛋白质×分钟）。此外，在喂食果糖的Tx大鼠心脏中可检测到肌球蛋白V1，但在喂食常规饮食的Tx大鼠中则不存在。为了确定果糖在不同甲状腺状态的动物中是否具有相似程度的影响，对Tx大鼠每日注射0.075、0.150、0.225和0.300微克T3/100克体重，并给予果糖或常规饮食。在每日接受0 - 0.15微克T3/100克体重的Tx大鼠中，果糖诱导的钙离子 - 肌球蛋白ATP酶活性增加幅度在24% - 27%之间。在每日接受0.225和0.300微克T3/100克体重的动物中，喂食果糖并未导致肌球蛋白ATP酶活性显著增加。这是因为甲状腺功能正常和甲状腺功能亢进动物的钙离子激活的肌球蛋白ATP酶活性彼此之间无显著差异。在接受60%葡萄糖饮食的甲状腺功能减退大鼠中，钙离子 - 肌球蛋白ATP酶活性比喂食常规饮食的Tx大鼠的值显著增加了20%。果糖和葡萄糖诱导的钙离子 - 肌球蛋白ATP酶活性变化发生在甲状腺激素或胰岛素水平未改变的情况下。我们的研究结果可能表明，心脏碳水化合物消耗会影响大鼠心脏中心室肌球蛋白同工酶的优势类型。
