Load Independence of Temperature-Dependent Ca2+ Recirculation Fraction in Canine Heart

Mizuno, Ju; Mohri, Satoshi; Shimizu, Juichiro; Suzuki, Shunsuke; Mikane, Takeshi; Araki, Junichi; Nishiyama, Tomoki; Hanaoka, Kazuo; Kajiya, Fumihiko; Suga, Hiroyuki

doi:10.2170/jjphysiol.54.319

Cited by 2 publications

(2 citation statements)

References 39 publications

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“…The simulation of myocardial relaxation suggests that the mechanoenergetics of cooled heart integratively account for the changes in the cooling-decelerated ATPase-dependent SR Ca 2+ sequestration and CB detachment (Mikane et al 1997). Further, by analyzing the transient alternans decay, we speculate that the recirculation fraction rate of internal Ca 2+ via SR becomes larger than Ca 2+ extrusion with cooling (Mizuno et al 2002(Mizuno et al , 2004. On the basis of contemporary reductionistic knowledge, the temperature sensitivities of all the Ca 2+ transporters are also comparable among themselves.…”

Section: Calcium Handling and Temperature Sensitivitymentioning

confidence: 75%

“…By definition, Q 10 is equal to the ratio of a variable M 10 value at temperature (t + 10) 8C to its M 0 value at t 8C, that is, Q 10 = M 10 /M 0 . In general, Q 10 2 of a variable evidently suggests that it is related directly or indirectly to a chemical process such as pump, channel, and exchange, whereas 1.5 Q 10 1 may be related to a physical process such as diffusion (Mizuno et al 2002(Mizuno et al , 2004.…”

Section: Temperature Coefficient (Q 10 )mentioning

confidence: 99%

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Half-logistic time constant: a more reliable lusitropic index than monoexponential time constant regardless of temperature in canine left ventricle

Mizuno

Matsubara

Mohri

et al. 2008

Can. J. Physiol. Pharmacol.

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Temperature changes influence cardiac diastolic function. The monoexponential time constant (tauE), which is a conventional lusitropic index of the rate of left ventricular (LV) pressure fall, increases with cooling and decreases with warming. We have proposed that a half-logistic time constant (tauL) is a better lusitropic index than tauE at normothermia. In the present study, we investigated whether tauL can remain a superior measure as temperature varies. The isovolumic relaxation LV pressure curves from the minimum of the first time derivative of LV pressure (dP/dtmin) to the LV end-diastolic pressure were analyzed at 30, 33, 36, 38, and 40 degrees C in excised, cross-circulated canine hearts. tauL and tauE were evaluated by curve-fitting using the least squares method and applying the half-logistic equation, P(t) = PA/[1 + exp(t/tauL)] + PB, and the monoexponential equation, P(t) = P0exp(-t/tauE) + Pinfinity. Both tauL and tauE increased significantly with decreasing temperature and decreased with increasing temperature. The half-logistic correlation coefficient (r) values were significantly higher than the monoexponential r values at the 5 above-mentioned temperatures. This implies that the superiority of the goodness of the half-logistic fit is not temperature dependent. The half-logistic model characterizes the amplitude and time course of LV pressure fall more reliably than the monoexponential model. Hence, we concluded that tauL is a more useful lusitropic index regardless of temperature.

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Section: Calcium Handling and Temperature Sensitivitymentioning

confidence: 75%

Section: Temperature Coefficient (Q 10 )mentioning

confidence: 99%

Half-logistic time constant: a more reliable lusitropic index than monoexponential time constant regardless of temperature in canine left ventricle

Mizuno

Matsubara

Mohri

et al. 2008

Can. J. Physiol. Pharmacol.

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Decay of postextrasystolic potentiation in the left and right ventricles of intact canine hearts

Black¹,

Ewert

Mulligan

2009

2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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Intracellular regulation of myocardial Ca2+ has long been of interest to physiologists. The force-interval relationship provides a phenomenological approach that permits insight into aspects of calcium regulation. The response to an extrasystole is a potentiation in contractile force and the recovery in contractile force is described by the recirculation fraction (RF). The RF provides a gross estimation of calcium uptake by sarcoplasmic reticulum (SR), leading to myocardial relaxation. The current study focused on the relationship of right (RV) and left ventricular (LV) RF in canines under several contractile states. Anesthetized canines (n = 5) were catheterized for RV and LV pressure measurements. dP/dt(max) for the RV and LV was calculated for three baseline beats, one extrasystole and the first five postextrasystolic beats. The relationship between the LV dP/dt(max) and RV dP/dt(max) for all of the mentioned beats was then examined. Contractility was increased with calcium chloride and extrasystoles were delivered. Once cardiac function returned to a baseline level, contractility was reduced by increasing the concentration of isoflurane and the evaluation repeated. All ventricular contractions were controlled by RA pacing to maintain intrinsic conduction. A strong linear relationship between RV and LV dP/dt(max) (r = 0.94 +/- .06) existed for most canine's contractile states. These results build on findings in isolated hearts and demonstrate that biventricular response to extrasystoles and subsequent contractile recovery is both linear and correlated, suggesting that intracellular calcium regulation in a given heart across contractile state is static.

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Load Independence of Temperature-Dependent Ca2+ Recirculation Fraction in Canine Heart

Cited by 2 publications

References 39 publications

Half-logistic time constant: a more reliable lusitropic index than monoexponential time constant regardless of temperature in canine left ventricle

Half-logistic time constant: a more reliable lusitropic index than monoexponential time constant regardless of temperature in canine left ventricle

Decay of postextrasystolic potentiation in the left and right ventricles of intact canine hearts

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