[Novel assessment of intracellular calcium transient decay in cardiac muscle by curve-fitting with half-logistic function].
A decrease in intracellular calcium (Ca2+) concentration in the cardiac muscle is one of the important factors to induce myocardial relaxation. A mono-exponential (m-E) function has been used for assessing myocardial relaxation curve of isometric tension and intracellular calcium transient (CaT) decay, and the m-E time constants for the relaxation curve of isometric tension (F tau E) and CaT decay (Ca tau E) have been recognised as lusitropic indices. However, we found that a half-logistic (h-L) function fits the relaxation curve of isometric tension much more precisely than the conventional m-E function in the ferret right ventricular (RV) papillary muscle. Moreover, we demonstrated that the goodness of the h-L fits for CaT decays was superior to the goodness of the m-E fits in the rabbit RV and murine left ventricular papillary muscles. The changes in the h-L time constants for the relaxation curves of isometric tension (F tau L) and CaT decays (Ca tau L) with the different onsets were significantly smaller than the changes in F tau E and Ca tau E, respectively. The differences in the h-L non-zero asymptotes for the relaxation curves of isometric tension and CaT decays with the different onsets were smaller than the changes in the m-E non-zero asymptotes. The h-L function model characterises the amplitudes and time courses of the relaxation curve of isometric tension and CaT decay more precisely than the m-E function model, and thus F tau L and Ca tau L serve as more novel and reliable lusitropic indices. Simultaneous analysis of myocardial relaxation curve of isometric tension and CaT decay using h-L functions can become a useful method for assessment of myocardial calcium handling.
Mizuno
Ju
J
Department of Anesthesiology, Teikyo University School of Medicine, Tokyo 173-8605.
Arita
Hideko
H
Hanaoka
Kazuo
K
Kusakari
Yoichiro
Y
Kurihara
Satoshi
S
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D016015:Logistic Models; D051379:Mice; D009126:Muscle Relaxation; D009206:Myocardium / Q000378:metabolism*; D011817:Rabbits
D002118:Calcium