Increased extracellular calcium concentrations in the isolated rat heart: effects on mitochondrial contact site formation.

In our previous study, mitochondrial creatine kinase (Mi-CK) activity is localised cytochemically in heart tissue. The activity was found to be exclusively localised in mitochondrial contact sites and the surface density of Mi-CK was increased upon myocardial stimulation (Biermans et al., 1989). As calcium is involved as an intracellular messenger of stimulation, we compared hearts noradrenaline-stimulated in vivo with isolated hearts perfused with buffers containing different calcium concentrations on the surface density Mi-CK.