Introduction: Mitochondrial diseases of the energy metabolism manifest as an impaired function of tissues with high energetic demands, especially the brain, heart, muscles and liver are affected. The diagnosis of mitochondrial disorders is especially based on the enzymatic assays in muscle tissue obtained on biopsy or in cultivated fibroblasts. The aim of our study was to find out whether isolated platelets are usable biological material for the measurement of activities of respiratory chain complexes. Material and methods: The investigated group consists of 161 individuals divided into four age groups. 32 children at the age of 0.5–2 years, 50 children from 3 to 9 years, 39 adolescents between 10 and 19 years and 40 young adults at the age of 20–35 years. Activities of respiratory chain complexes I, II, III, IV and I+III and citrate synthase (CS) were investigated spectrophotometrically in platelets isolated from the peripheral blood. Results: The reference ranges for activities of the respiratory chain complexes I, II, III, IV and I+III and citrate synthase in isolated platelets were obtained for each of the age groups. No differences in the activities of respiratory chain complexes and CS were found between men and women but a significant relationship between the activity of citrate synthase and the age of the investigated subjects was found (y = 72.91±0.305 x, P < 0.05). Conclusion: Isolated platelets contribute only very little to the overall metabolic turnover but because of their easy availability they may serve as a suitable material for analysis of activities of respiratory chain complexes. We suppose that the analysis of activities of respiratory chaincomplexes can be useful for the enzymatic diagnosis of specific mitochondrial disorders with a generalized affection.

        Key words: mitochondria, thrombocytes, respiratory chain.