Mitochondrial involvement in carbachol-induced intracellular Ca2+ mobilization and contraction in rat gastric smooth muscle

Mitochondria are important modulators of Ca2+ homeostasis. However, it is not clear if they modulate and participate in smooth muscle signaling and contraction. The aim of the present work was to investigate the role of mitochondria in Ca2+ transients and contraction induced by metabotropic muscarinic receptor activation in rat gastric smooth muscle. Carbachol (CCh)-induced contraction was investigated in the absence or presence of increasing concentration of mitochondrial protonophore, carbonyl cyanide p-(trifluoro-methoxy)phenyl-hydrazone (FCCP), in gastric fundus strips. Ca2+ and mitochondrial membrane potential (ΔΨm) measurements were performed in primarily cultured gastric smooth muscle cells loaded with FURA-2 or TMRE dyes. Results show that CCh (1μM)-induced contraction was inhibited by FCCP in a concentration-dependent manner. In cultured smooth muscle cells CCh (1μM) caused a cytosolic Ca2+ rise. Preincubation with FCCP strongly inhibited CCh-evoked Ca2+ transients indicating that mitochondria shape intracellular Ca2+ signals. CCh induced elevations of ∆Ψm in 60% of the individual mitochondrion analyzed. Taken together our results indicate that CCh induces release of Ca2+ from intracellular stores, which may be modulated by mitochondria. Thus, mitochondria participate of the intracellular Ca2+ homeostasis in muscarinic contraction in gastric fundus smooth muscle.