FIGURE 3.

Relationship between membrane potential and respiratory flux upon changes in adenine nucleotide translocator activity. The changes in respiration rate, V_O2, and membrane potential, ΔΨ_m, are determined by the behavior of the whole model according to a steady-state analysis performed at different adenine nucleotide translocator maximal activities (V_maxANT) which result in different ADP_m concentrations (A, inset). The left portion of curves a and b in panels A and B, corresponds to mitochondria in state 4 (i.e., low ADP) and the increases in V_O2 result from the respiratory control exerted by increasing ADP concentrations. The simulations were run with the following parameter values: (a) ΔpH = −0.6; ρ^res = 0.00072 mM; ADP_i = 0.05 mM; mM s⁻¹; ρ^F1 = 1.216 mM; [Ca²⁺]_i = 0.1 μM; g_H = 0.01 mM s⁻¹ V⁻¹; AcCoA = 1.0 mM. V_maxANT is varied in the range 0.01–25 mM s⁻¹; (b) all parameters are the same as in a, except for ρ^res = 0.0051 mM and ρ^F1 = 0.61 mM. The remainder of the parameters are reported in Table 3. (C) Changes in the relationship between ΔΨ_m and the respiratory rate obtained at various ratios of creatine/creatine phosphate in a preparation of heart mitochondria with normal or reduced respiratory activity (left-shifted curves). Redrawn from Borutaite et al. (1995).