REFERENCE CHARTS FOR RESPIRATORY-CHAIN ACTIVITIES IN HUMAN TISSUES

This paper presents a collection of quantitative values for respirator y chain activities in human tissues. These were measured in the most w idely used tissues in screening procedures for respiratory chain defic iencies. Investigations were mainly carried out using the different st andardized micro-methods previously detailed (Rustin et al., Clin Chim Acta, 1994). The potential effect of the age of the patients on both absolute and relative levels of respiratory chain activities in their skeletal muscle tissue was first considered. No evidence for any signi ficant difference between the various age groups in the studied popula tion (ranging from 0 to above 50 years of age) was observed. Moreover, a quite similar picture of the organization of the respiratory chain was suggested independent of the tissue or the cells investigated. In particular, it was found that roughly identical enzyme activity ratios could be measured in all tissues, which allowed study of the differen tial involvement of organs and tissues in patients potentially affecte d by a respiratory chain deficiency. Some tissue-specific features wer e, however, observed, including varying rates of glycerol-3-phosphate dehydrogenase activities and increased succinate dehydrogenase activit y in liver. The technical limitations remaining in the investigations of respiratory chain disorders in man are discussed in the conclusion.