Half-Logistic Function Model for First Half of Descending Phase of Cardiomyocyte Cytoplasmic Ca(2+) Concentration ([Ca(2+)]i)-Time Curve (CaTCIII) in Isolated Aequorin-Injected Mouse Left Ventricular Papillary Muscle.
BACKGROUND
Myocardial contraction and relaxation are regulated by increases and decreases in cytoplasmic calcium concentration ([Ca(2+)]i). In previous studies, we found that a half-logistic (h-L) function, which represents a half-curve of a symmetrical sigmoid logistic function with a boundary at the inflection point, curve-fits the first half of the ascending phase and the second half of the descending phase of the [Ca(2+)]i transient curve better than a mono-exponential (m-E) function. In the present study, we investigated the potential application of an h-L function to analyse the first half of the descending phase of CaTC (CaTCIII).


METHODS
The [Ca(2+)]i was measured using the Ca(2+)-sensitive aequorin, which was microinjected into 15 isolated mouse left ventricular (LV) papillary muscles. The observed CaTCIII data in the interval from the point corresponding to the peak [Ca(2+)]i to the point corresponding to dCa/dtmin was curve-fitted using the h-L and m-E function equations by the least-squares method.


RESULTS
The mean correlation coefficient (r) values of the h-L and m-E function best curve-fits for 11 CaTCIIIs were 0.9986 and 0.9982, respectively. The Z transformation of h-L r (3.64 ± 0.45) was larger than that of m-E r (3.50 ± 0.33) (p < 0.05).


CONCLUSIONS
The h-L function can evaluate most CaTCIIIs more accurately than the m-E function in isolated aequorin-injected mouse LV papillary muscle. The three calculated h-L parameters i.e., amplitude constant, time constant, and non-zero asymptote, are more reliable indices than m-E for evaluating the magnitude and time course of the change in the decrease in [Ca(2+)]i.


BACKGROUND
Ca(2+) transient; Half-logistic amplitude constant; Half-logistic non-zero asymptote; Half-logistic time constant; Myocardial Ca(2+) handling.
Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8549; ; Department of Anesthesiology and Pain Medicine, Juntendo University Faculty of Medicine, Tokyo 113-8431; ; Department of Dental Anesthesiology, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582; ; Department of Anesthesiology and Pain Relief Center, JR Tokyo General Hospital, Tokyo 151-8528, Japan.
Ju
J
Mizuno
Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8549;
Mikiya
M
Otsuji
Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8549; ; Department of Dental Anesthesiology, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582;
Takeshi
T
Yokoyama
Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8549; ; Department of Anesthesiology and Pain Relief Center, JR Tokyo General Hospital, Tokyo 151-8528, Japan.
Hideko
H
Arita
Department of Anesthesiology, Faculty of Medicine, The University of Tokyo, Tokyo 113-8549; ; Department of Anesthesiology and Pain Relief Center, JR Tokyo General Hospital, Tokyo 151-8528, Japan.
Kazuo
K
Hanaoka