class="enumerated" style="list-style-type:decimal">Our goal in this study was to evaluate the effect of haemodynamic overload on cross-bridge (XBr) kinetics in the rabbit heart independently of myosin heavy chain (MHC) isoforms, which are known to modulate kinetics in small mammals. We applied a myothermal-mechanical protocol to isometrically contracting papillary muscles from two rabbit heart populations: (1) surgically induced right ventricular pressure overload (PO), and (2) sustained treatment with propylthiouracil (PTU). Both treatments resulted in a 100 % V3 MHC profile.XBr force–time integral (FTI), evaluated during the peak of the twitch from muscle FTI and tension-dependent heat, was greater in the PO hearts (0.80 ± 0.10 versus 0.45 ± 0.05 pN s, means ±s.e.m.., P = 0.01).Within the framework of a two-state XBr model, the PO XBr developed more force while attached (5.8 ± 0.9 versus 2.7 ± 0.3 pN), with a lower cycling rate (0.89 ± 0.10 versus 1.50 ± 0.14 s−1) and duty cycle (0.14 ± 0.03 versus 0.24 ± 0.02).Only the ventricular isoforms of myosin light chain 1 and 2 and cardiac troponin I (cTnI) were expressed, with no difference in cTnI phosphorylation between the PO and PTU samples. The troponin T (TnT) isoform compositions in the PO and PTU samples were significantly different (P = 0.001), with TnT2 comprising 2.29 ± 0.03 % in PO hearts versus 0.98 ± 0.01 % in PTU hearts of total TnT.This study demonstrates that MHC does not mediate dramatic alterations in XBr function induced by haemodynamic overload. Our findings support the likelihood that differences among other thick and thin filament proteins underlie these XBr alterations.
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机译:class =“ enumerated” style =“ list-style-type:decimal”> <!-list-behavior =枚举前缀-word = mark-type = decimal max-label-size = 0-> 我们在这项研究中的目标是评估血流动力学超负荷对兔心脏中跨桥(XBr)动力学的影响,而与肌球蛋白重链(MHC)亚型无关,后者已知会调节小型哺乳动物的动力学。我们应用了肌热力学方案,对来自两个兔子心脏群的乳头肌进行等轴测收缩:(1)手术引起的右心室压力超负荷(PO),以及(2)丙硫氧嘧啶(PTU)持续治疗。两种处理均产生100%的V3 MHC曲线。 li> XBr力-时间积分(FTI),在肌肉FTI抽搐高峰和张力依赖的热期间评估,在PO心脏中更大( 0.80±0.10 vs 0.45±0.05 pN s,平均值为±sem。,P = 0.01)。 li> 在两态XBr模型的框架内,PO XBr附着时产生的力更大(5.8±0.9) vs. 2.7±0.3 pN)和更低的循环速率(0.89±0.10 vs 1.50±0.14 s -1 sup>)和占空比(0.14±0.03 vs 0.24±0.02)。 li>