An Attempt at the Cytochemical Localization of Citrate Synthase in Rat Heart Muscle

Abstract

Most of the Krebs cycle enzymes are believed to exist in ‘soluble’ form in the mitochondrial matrix except succinate dehydrogenase which is a part of the inner membrane (1). Citrate synthase, one of the Krebs cycle enzymes, is present in rat liver, kidney and heart mitochondria proportional to the amount of the inner membrane area rather than the matrix volume (2). Recent studies on model systems support the idea that the ‘soluble’ Krebs cycle enzymes are probably localized on the inner surface (matrix side) of the inner membrane (3-5). Localization of these enzymes in mitochondria by cytochemical or immunocytochemical methods would be crucial to determine the validity of the above hypothesis. The present study describes cytochemical localization of citrate synthase in rat heart muscle.