title: Structural differences in two biochemically defined populations of cardiac mitochondria.
abstract: To determine whether there are structural differences in two topologically separated, biochemically defined mitochondrial populations in rat heart myocytes, the interior of these organelles was examined by high-resolution scanning electron microscopy. On the basis of a count of 159 in situ subsarcolemmal mitochondria (SSM, i.e., those that directly abut the sarcolemma), these organelles possess mainly lamelliform cristae (77%), whereas the cristae in in situ interfibrillar mitochondria (IFM, i.e., those situated between the myofibrils, n = 300) are mainly tubular (55%) or a mixture of tubular and lamelliform (24%). Isolated SSM (n = 374), similar to their in situ counterparts, have predominantly lamelliform cristae (75%). The proportions of crista types in isolated IFM (n = 337) have been altered, with only 20% of these organelles retaining exclusively tubular cristae, whereas 58% are mixed; of the latter, lamelliform cristae predominate. This finding suggests that, in contrast to SSM, the cristae in IFM are structurally plastic, changing during isolation. These observations on >1,000 organelles provide the first quantitative morphological evidence for definitive differences between the two populations of cardiac mitochondria.
authors.affiliation: Department of Cytomorphology, School of Medicine, University of Cagliari, Cagliari, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Riva
authors.forename: Bernard
authors.initials: B
authors.lastname: Tandler
authors.forename: Felice
authors.initials: F
authors.lastname: Loffredo
authors.forename: Edwin
authors.initials: E
authors.lastname: Vazquez
authors.forename: Charles
authors.initials: C
authors.lastname: Hoppel
mesh_terms: D000818:Animals; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008929:Mitochondria, Heart / Q000378:metabolism / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley