Kinetics of Mitochondrial Calcium Transport 11. A KINETIC DESCRIPTION OF THE SODIUM-DEPENDENT CALCIUM EFFLUX MECHANISM OF LIVER MITOCHONDRIA AND INHIBITION BY RUTHENIUM RED AND BY TETRAPHENYLPHOSPHONIUM*
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چکیده
Sodium-dependent calcium efflux from rat liver mitochondria has been studied as a function of mitochondrial calcium loads (2 to 40 nmol/mg) and extramitochondrial sodium concentrations (5 to 40 mM). The resulting data can be fit to a terreactant model which exhibits simultaneous kinetics (Le. both sodium and calcium must be bound simultaneously for transport to occur). The Hill coefficients for the calcium and sodium dependences were 1.0 & 0.1 and 2.0 & 0.2, respectively. The cooperativity of the sodium dependence allows the terreactant model to be reduced to a bireactant model in which the sodium concentration only appears mathematically as the square of the sodium concentration. The data then fit the relationship
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