Samuel J L, Marotte F, Delcayre C, Rappaport L
Am J Physiol. 1986 Dec;251(6 Pt 2):H1118-25. doi: 10.1152/ajpheart.1986.251.6.H1118.
Since stimulation of heart hypertrophy by pressure overload was previously shown to be accompanied by a densification of microtubule network in rat heart myocytes, we verified that similar process occurred during postnatal growth in euthyroid rats and in hypothyroid rats whose growth was stimulated by 4 micrograms/day L-thyroxine (T4). For this purpose, tubulin, the constituent protein of microtubules, was immunolabeled in myocytes isolated at various times after birth. Myocyte hypertrophy was evaluated by myocyte size, the number of nuclei per cell and isomyosin expression. In hypothyroid rats, the microtubule network, which was underdeveloped, was most dense around the nucleus. During the phase of fast myocyte hypertrophy observed in euthyroid rats during late postnatal development and in hypothyroid rats after T4 administration, transient microtubule densification occurred in a myocyte subpopulation in which size was mainly determined by the rate of myocyte hypertrophy. The densification process and its kinetics resembled those observed when heart hypertrophy was induced by pressure overload. It is concluded that in rat heart myocytes undergoing hypertrophy, microtubule densification might be related to fast sarcomerogenesis, whether the stimulus is mechanical (e.g., pressure overload) or hormonal (e.g., T4).
由于先前已表明压力超负荷刺激心脏肥大伴随着大鼠心肌细胞微管网络的致密化，我们验证了在甲状腺功能正常的大鼠以及通过每天4微克L-甲状腺素（T4）刺激生长的甲状腺功能减退大鼠的出生后生长过程中，是否发生了类似的过程。为此，在出生后不同时间分离的心肌细胞中对微管的组成蛋白微管蛋白进行了免疫标记。通过心肌细胞大小、每个细胞的核数量和同工肌球蛋白表达来评估心肌细胞肥大。在甲状腺功能减退的大鼠中，发育不全的微管网络在细胞核周围最为致密。在甲状腺功能正常的大鼠出生后晚期发育期间以及甲状腺功能减退的大鼠给予T4后观察到的快速心肌细胞肥大阶段，在一个心肌细胞亚群中发生了短暂的微管致密化，该亚群的大小主要由心肌细胞肥大率决定。致密化过程及其动力学类似于压力超负荷诱导心脏肥大时观察到的情况。结论是，在经历肥大的大鼠心肌细胞中，无论刺激是机械性的（如压力超负荷）还是激素性的（如T4），微管致密化可能与快速肌节形成有关。
