ENZYMATIC-ACTIVITIES OF MITOCHONDRIAL RESPIRATORY COMPLEXES FROM CHILDREN MUSCULAR BIOPSIES - AGE-RELATED EVOLUTIONS

Measurements were performed to determine maximum enzymatic activities of citrate synthetase and respiratory complexes I, III, and IV of mito chondria obtained from muscular biopsies in control children. The sign ificant number of determinations carried out (43 different biopsies in controls aged 3.8 to 19.1 years) permits the formulation of a table o f statistically validated reference values for these activities. These values are independent of sex of the controls, and of the studied mus cles. Citrate synthetase activity, which remains stable in this age ra nge, thus constitutes a good internal indicator of mitochondrial activ ity. Complexes I and III manifest activity which does not vary with ag e. On the other hand, cytochrome oxidase activity shows a highly signi ficant decrease in this age group. This decrease may be correlated wit h qualitative changes (subunits VIa and VIIa) in composition of this c omplex.