Objective: To study the mitochondrial respiratory chain enzyme activities in patients with idiopathic dilated cardiomyopathy (IDC).
Methods: Mitochondrial respiratory chain enzyme activities were assessed spectrophotometrically in left ventricular tissue of 17 patients with IDC undergoing cardiac transplantation, as well as in two groups of controls: a group of six patients suffering from ischemic dilated cardiomyopathy (IC) also undergoing cardiac transplantation, and a group of 17 organ donors considered normal from a cardiac point of view. Cytochrome b gene from three IDC patients whose complex III activity was particularly low and from three controls was also sequenced.
Results: We found that complex III enzymatic activity was lower not only in IDC but also in IC patients when compared with normal controls. When analysing cytochrome b gene we only found neutral polymorphisms previously described.
Conclusions: In view of such results, we believe that the decrease of respiratory chain complex III activity found in some cases of IDC is a secondary phenomenon, and not due to a primary mitochondrial disease.