Sakamoto T, Matsubara H, Hata Y, Shimizu J, Araki J, Takaki M, Suga H
Department of Physiology II, Okayama University Medical School, Japan.
Heart Vessels. 1996;11(4):171-9. doi: 10.1007/BF02559989.
We found that the isovolumic pressure-time curve of the canine left ventricle closely fitted the difference of two logistic function curves and that the isovolumic relaxation-pressure curve segment was more reliably characterized by a logistic time constant than by the conventional exponential time constant. We therefore hypothesized that the calcium (Ca) transient and the Ca-troponin (Tn) binding and crossbridge (CB) kinetics underlay the logistic character of the ventricular isovolumic pressure curve. We tested this hypothesis with a computer simulation of a simple Ca and CB kinetics model of myocardial isometric twitch force development. We assumed the instantaneous number of attached CBs that was theoretically given as the difference between the cumulative CB attachment and detachment curves. We radically changed the Ca transient, Ca-Tn binding, and CB kinetic parameters. We always found that both the cumulative CB attachment and detachment curves closely fitted logistic functions. The difference curve of these two best-fit logistic functions closely fitted the theoretical F curve with certain combinations of the Ca transient, the Ca-Tn binding, and the CB kinetic parameters. These results seem to support our hypothesis.
我们发现犬左心室的等容压力-时间曲线紧密拟合两条逻辑函数曲线的差值，并且等容舒张压力曲线段用逻辑时间常数比用传统指数时间常数能更可靠地表征。因此，我们推测钙（Ca）瞬变、钙-肌钙蛋白（Tn）结合及横桥（CB）动力学是心室等容压力曲线逻辑特征的基础。我们用一个简单的心肌等长收缩力发展的Ca和CB动力学模型进行计算机模拟来验证这一假设。我们假定理论上给出的附着CB的瞬时数量为累积CB附着和脱离曲线的差值。我们彻底改变了Ca瞬变、Ca-Tn结合及CB动力学参数。我们总是发现累积CB附着和脱离曲线都紧密拟合逻辑函数。这两条最佳拟合逻辑函数的差值曲线在Ca瞬变、Ca-Tn结合及CB动力学参数的某些组合下紧密拟合理论F曲线。这些结果似乎支持了我们的假设。
