Mizuno Ju, Otsuji Mikiya, Takeda Kenji, Yamada Yoshitsugu, Arita Hideko, Hanaoka Kazuo, Hirano Shuta, Kusakari Yoichiro, Kurihara Satoshi
Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Japan.
Int Heart J. 2007 Mar;48(2):215-32. doi: 10.1536/ihj.48.215.
A decrease in myocardial intracellular calcium concentration (Ca(2+)) precedes relaxation, and a monoexponential function is typically used for fitting the decay of the Ca(2+) transient. However, a logistic function has been shown to be a better fit for the relaxation force curve, compared to the conventional monoexponential function. In the present study, we compared the logistic and monoexponential functions for fitting the Ca(2+) declines, which were measured using the aequorin method, and isometric relaxation force curves at 4 different onsets: the minimum time-derivative of Ca(2+) (dCa(2+)/dt (min)) and force (dF/dt(min)), and the 10%, 20% and 30% lower Ca(2+) levels and forces over the data-sampling period in 7 isolated rabbit right ventricular and 15 isolated mouse left ventricular papillary muscles. Logistic functions were significantly superior for fitting the [Ca(2+)] (i) declines and relaxation force curves, compared to monoexponential functions. Changes in the normalized logistic [Ca(2+)] (i) decline and relaxation force time constants at the delayed onsets relative to their 100% values at d[Ca(2+)] (i)/dt(min) and dF/dt(min) were significantly smaller than the changes in the normalized monoexponential time constants. The ratio of the logistic relaxation force time constant relative to the logistic Ca(2+) decline time constant was significantly smaller in mouse than in rabbit. We conclude that the logistic function more reliably characterizes the Ca(2+) decline and relaxation force curve at any onset, irrespective of animal species. Simultaneous analyses using the logistic model for decay of the Ca(2+) transient and myocardial lusitropism might be a useful strategy for analysis of species-specific myocardial calcium handling.
心肌细胞内钙浓度（Ca(2+)）的降低先于舒张，并且通常使用单指数函数来拟合Ca(2+)瞬变的衰减。然而，与传统的单指数函数相比，逻辑函数已被证明更适合拟合舒张力量曲线。在本研究中，我们比较了逻辑函数和单指数函数对Ca(2+)下降的拟合情况，Ca(2+)下降是使用水母发光蛋白方法测量的，并且在4个不同起始点比较了等长舒张力量曲线：Ca(2+)的最小时间导数（dCa(2+)/dt (min)）和力量（dF/dt(min)），以及在7个离体兔右心室和15个离体小鼠左心室乳头肌的数据采样期内低于Ca(2+)水平和力量10%、20%和30%的点。与单指数函数相比，逻辑函数在拟合Ca(2+)下降和舒张力量曲线方面明显更优。相对于在dCa(2+)/dt(min)和dF/dt(min)时的100%值，延迟起始点处归一化的逻辑Ca(2+)下降和舒张力量时间常数的变化明显小于归一化单指数时间常数的变化。小鼠中逻辑舒张力量时间常数相对于逻辑Ca(2+)下降时间常数的比率明显小于兔子。我们得出结论，无论动物物种如何，逻辑函数都能更可靠地表征任何起始点处的Ca(2+)下降和舒张力量曲线。使用逻辑模型同时分析Ca(2+)瞬变的衰减和心肌舒张性能可能是分析物种特异性心肌钙处理的一种有用策略。
