Cross-talk between the sarcoplasmic reticulum and the mitochondrial calcium handling systems may play an important role in the regulation of contraction in anococcygeus smooth muscle

Mitochondrial Ca2+ and its relation with the contraction induced by phenylephrine was investigated. In normal Ca2+, carbonyl cyanide p-(trifluoro-methoxy)phenyl-hydrazone (FCCP) and oligomycin produced contraction similar to that promoted by phenylephrine. Phenylephrine-induced contraction was reduced by FCCP+oligomycin. In Ca2+-free, FCCP+oligomycin did not induce contraction. Response to FCCP+oligomycin was reduced upon Ca2+ repletion and this response was lower than that to phenylephrine. Ca2+ concentration was increased by FCCP+oligomycin. Since a profuse net of sarcoplasmic reticulum encloses mitochondria, a cross-talk between the two organelles may play an important role in the phenylephrine-induced contraction in presence of Ca2+ encountered in both sarcoplasmic reticulum and extracellular medium of anococcygeus cells.