Va. Selivanov et al., A MODEL OF MITOCHONDRIAL CA2-INDUCED CA2+ RELEASE SIMULATING THE CA2+OSCILLATIONS AND SPIKES GENERATED BY MITOCHONDRIA(), Biophysical chemistry, 72(1-2), 1998, pp. 111-121
Recent evidence underlines a key role of mitochondrial Ca2+ fluxes in
cell Ca2+ signalling. We present here a kinetic model simulating the C
a2+ fluxes generated by mitochondria during mitochondrial Ca2+-induced
Ca2+ release (mCICR) resulting from the operation of the permeability
transition pore (PTP). Our model connects the Ca2+ fluxes through the
ruthenium red-sensitive Ca2+ uniporter, the respiration-dependent and
passive HC fluxes, the rate of oxygen consumption, the movements of w
eak acids across the mitochondrial membrane, the electrical transmembr
ane potential (Delta Psi), and operation of the PTP. We find that two
factors are crucial to account for the various mCICR profiles that can
be observed experimentally: (i) the dependence of PTP opening and clo
sure on matrix pH (pH(i)), and (ii) the relative inhibition of the res
piratory rate consecutive to PTP opening. The resulting model can simu
late irreversible Ca2+ efflux from mitochondria, as well as the genesi
s of damped or sustained Ca2+ oscillations, and of single Ca2+ spikes.
The model also simulates the main features of mCICR, i.e. the thresho
ld-dependence of mCICR triggering, and the all-or-nothing nature of mC
ICR operation. Our model should appear useful to further mathematicall
y address the consequences of mCICR on the spatiotemporal organisation
of Ca2+ signals, as a 'plug-in' module for the existing models of cel
l Ca2+ signalling. (C) 1998 Elsevier Science B.V. All rights reserved.