Sheer D, Morkin E
J Pharmacol Exp Ther. 1984 Jun;229(3):872-9.
The effects on ventricular myosin isoenzyme expression of naturally occurring and synthetic thyroid analogs (3,5,3'-L-triiodothyronine, 3,5,3'-D-triiodothyronine, 3,3',5'-L- triiodothyronine , 3,5,3'-L-triiodothyroacetic acid and 3,5-L-diiodothyronine), catecholamines and high carbohydrate diets have been studied in thyroidectomized and hypophysectomized rats. Also, the effects on myosin isoenzyme expression of adrenalectomy and hydrocortisone replacement have been studied in euthyroid animals. Myocardial CO2 production and hepatic alpha-glycerolphosphate dehydrogenase activity were measured to monitor the effects of these interventions on tissue respiration. The results indicate that there was no significant separation between the actions of thyroid analogs on metabolic parameters and myosin isoenzyme patterns. However, high carbohydrate feeding in hypophysectomized rats increased the isoenzyme V1 from 12% to about 36% of total myosin; partial replacement with 3,5,3'-L-triiodothyronine and fructose feeding had synergistic actions. In thyroidectomized rats, feeding a high carbohydrate diet increased the V1 form from undetectable levels to about 28% of total myosin; partial 3,5,3'-L-triiodothyronine replacement had an additive effect. Beta adrenergic stimulation with isoproterenol and blockade with propranolol did not affect myosin isoenzyme expression. Adrenalectomy in euthyroid rats caused a 33% decrease in the V1 form and a corresponding increase in the V3 isoenzyme, which could be reversed by treatment with hydrocortisone. Thus, thyroid analogs do not selectively stimulate myosin isoenzyme expression as compared with their effects on energy production. Furthermore, the results suggest that the mechanism for regulation of cardiac myosin isoenzymes may involve a primary signal related to dietary carbohydrate, which is modulated by thyroid hormone, and possibly glucocorticoids.
在甲状腺切除和垂体切除的大鼠中，研究了天然存在的和合成的甲状腺类似物（3,5,3'-L-三碘甲状腺原氨酸、3,5,3'-D-三碘甲状腺原氨酸、3,3',5'-L-三碘甲状腺原氨酸、3,5,3'-L-三碘甲状腺乙酸和3,5-L-二碘甲状腺原氨酸）、儿茶酚胺和高碳水化合物饮食对心室肌球蛋白同工酶表达的影响。此外，在甲状腺功能正常的动物中，研究了肾上腺切除术和氢化可的松替代对肌球蛋白同工酶表达的影响。测量心肌二氧化碳产生量和肝脏α-甘油磷酸脱氢酶活性，以监测这些干预措施对组织呼吸的影响。结果表明，甲状腺类似物对代谢参数和肌球蛋白同工酶模式的作用之间没有显著差异。然而，垂体切除的大鼠喂食高碳水化合物后，同工酶V1从总肌球蛋白的12%增加到约36%；用3,5,3'-L-三碘甲状腺原氨酸部分替代和喂食果糖具有协同作用。在甲状腺切除的大鼠中，喂食高碳水化合物饮食使V1形式从不可检测水平增加到总肌球蛋白的约28%；3,5,3'-L-三碘甲状腺原氨酸部分替代具有累加效应。用异丙肾上腺素进行β-肾上腺素能刺激和用普萘洛尔进行阻断不影响肌球蛋白同工酶表达。甲状腺功能正常的大鼠肾上腺切除导致V1形式减少33%，V3同工酶相应增加，用氢化可的松治疗可逆转这种变化。因此，与甲状腺类似物对能量产生的影响相比，它们不会选择性地刺激肌球蛋白同工酶表达。此外，结果表明，心肌肌球蛋白同工酶的调节机制可能涉及与饮食碳水化合物相关的初级信号，该信号受甲状腺激素以及可能的糖皮质激素调节。
