Mizuno Ju, Morita Shigeho, Araki Junichi, Otsuji Mikiya, Hanaoka Kazuo, Kurihara Satoshi
Department of Anesthesiology, Teikyo University School of Medicine, Tokyo 173-8605.
Masui. 2009 Jan;58(1):67-76.
As the left ventricular (LV) pressure curve and myocardial tension curve in heart are composed of contraction and relaxation processes, we have found that hybrid logistic (HL) function calculated as the difference between two logistic functions curve-fits better the isovolumic LV pressure curve and the isometric twitch tension curve than the conventional polynomial exponential and sinusoidal functions. Increase and decrease in intracellular Ca2+ concentration regulate myocardial contraction and relaxation. Recently, we reported that intracellular Ca2+ transient (CaT) curves measured using the calcium-sensitive bioluminescent protein, aequorin, were better curve-fitted by HL function compared to the polynomial exponential function in the isolated rabbit RV and mouse LV papillary muscles. We speculate that the first logistic component curve of HL fit represents the concentration of the Ca2+ inflow into the cytoplasmic space, the concentration of Ca2+ released from sarcoplasmic reticulum (SR), the concentration of Ca2+ binding to troponin C (TnC), and the attached number of cross-bridge (CB) and their time courses, and that the second logistic component curve of HL fit represents the concentration of Ca2+ sequestered into SR, the concentration of Ca2+ removal from the cytoplasmic space, the concentration of Ca2+ released from TnC, and the detached number of CB and their time courses. This HL approach for CaT curve may provide a more useful model for investigating Ca2+ handling, Ca(2+) -TnC interaction, and CB cycling.
由于心脏中的左心室（LV）压力曲线和心肌张力曲线由收缩和舒张过程组成，我们发现，通过两个逻辑函数之差计算得到的混合逻辑（HL）函数，比传统的多项式指数函数和正弦函数，能更好地拟合等容LV压力曲线和等长收缩张力曲线。细胞内Ca2+浓度的升高和降低调节心肌的收缩和舒张。最近，我们报道，在分离的兔右心室和小鼠左心室乳头肌中，与多项式指数函数相比，使用钙敏感生物发光蛋白水母发光蛋白测量的细胞内Ca2+瞬变（CaT）曲线，能被HL函数更好地拟合。我们推测，HL拟合的第一个逻辑成分曲线代表流入细胞质空间的Ca2+浓度、从肌浆网（SR）释放的Ca2+浓度、与肌钙蛋白C（TnC）结合的Ca2+浓度以及横桥（CB）的附着数量及其时间进程，而HL拟合的第二个逻辑成分曲线代表被隔离到SR中的Ca2+浓度、从细胞质空间去除的Ca2+浓度、从TnC释放的Ca2+浓度以及CB的脱离数量及其时间进程。这种用于CaT曲线的HL方法可能为研究Ca2+处理、Ca(2+)-TnC相互作用和CB循环提供一个更有用的模型。
