Figure 3.

Successive additions of Ca${}^{2+}$ leading to mPTP opening in experiments and in the model. (A) Experiment performed in a suspension of mitochondria extracted from rat hepatocytes. The [Ca${}^{2+}$]${}_{\mathrm{e}\mathrm{m}}$ is monitored by fluorescence using 5 $\mu M$ Fluo-4. Following the addition of five Ca${}^{2+}$ pulses (blue arrows), the mPTP opens, as attested by the sudden rise in Ca${}^{2+}$ concentration in the medium. (B) Simulations of the five-variable model (Eqs. 1 and 4–7). The model successfully reproduces the [Ca${}^{2+}$]${}_{\mathrm{e}\mathrm{m}}$ behaviour (in blue), in response to the Ca${}^{2+}$ pulses (implemented with $J_{in}$). The final increase in the $C_{em}$ is associated with a sudden increase in mPTP opening (variable $PTP$, standing for the fraction of open PTP, in red) and a fall in $\mathrm{\Delta }\mathrm{\Psi }$ (in yellow). See Table S1 for parameter values.