The respiratory chain is a mosaic of complexes functionally linked through the mobile intermediates ubiquinone and cytochrome c. Changes in content of complexes that are not rat-limiting might not be reflected in the overall respiratory rate but may be revealed by titration with specific inhibitors. Oxidation of succinate by membranes of liver mitochondria from fetal, adult and starved rats was titrated with antimycin. Initial respiratory rates were similar but antimycin-titration curves were markedly different. The results indicate that the content of Complex III (cytochrome b-c1 span) is much lower in mitochondria from fetal and starved adult rats than in controls. In no case however is Complex III initially rat-limiting, and in fetal and starved adult rats it seems that a much lower content of functional Complex III is required to sustain a given respiratory rate. A possible explanation is a compensatory optimization of the pool function of ubiquinone, through increases in its content or its mobility in the mitochondrial membrane.

Aging↗

PubMedDate not supplied

Mitochondrial antibodies in primary biliary cirrhosis: species and nonspecies specific determinants of M2 antigen.

Sera from patients with primary biliary cirrhosis reacted with four major bands in beef heart mitochondria and ATPase extract when analyzed by immunoblot after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These four immunologically reactive bands corresponded to protein bands with molecular weights of about (a) 80,000; (b) 63,000; (c) 56,000; and (d) 43,000 to 46,000. An additional immunoreactive band was found with some high-titered primary biliary cirrhosis sera at 36,000. No association with any ATPase subunits was found, except for band c which migrated between the alpha- and beta-subunit of ATPase. Most ATPase fractions did not contain this band c, indicating that M2 determinants, as defined by immunoblot, are not identical with any ATPase subunit. Species and nonspecies-specific determinants of M2 were identified using mitochondria from rat liver and human heart and liver. Antigenic bands a, c and d were nonspecies-specific. Band b and e occurred only in beef heart. An additional determinant at about 38,000 was detected using human heart and liver mitochondria. Primary biliary cirrhosis sera showed a typical reaction with two protein bands of Escherichia coli, one at about 85,000 to 90,000 and the other at 60,000. Antibodies against both determinants could be absorbed with submitochondrial particles of beef heart showing that E. coli shares cross-reacting determinants with mitochondria. Sera from 56 primary biliary cirrhosis patients were tested using beef heart mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗