Figure 2.

Mitochondria contribute to [Ca²⁺]_c decline following voltage-dependent Ca²⁺ entry in smooth muscle. (A) Depolarization (−70 to 0 mV) activated a voltage-dependent Ca²⁺ current (data not shown) and increased [Ca²⁺]_c in a single colonic myocyte. CCCP (5 μM) slowed the rate of decline of [Ca²⁺]_c on repolarization compared with control. (B) The rate of decline (−d[Ca²⁺]_c/dt), obtained from high order polynomial fits to the declining phase of the transients, shows a significant slowing when mitochondria were prevented from accumulating Ca²⁺. (C) A summary of the rates of decline for 10 cells in the presence and absence of CCCP. The inferred mitochondrial contribution to the decline of [Ca²⁺]_c (red line) was obtained by subtracting control rates from those seen in CCCP and shows that mitochondrial Ca²⁺ uptake occurred above 200 nM [Ca²⁺]_c (from McCarron & Muir ⁴⁹ with permission).