title: Numerical densities of intramembrane particles in the cardiac sarcolemma of normal and myopathic Syrian hamsters.
abstract: The purpose of this study was to examine the density of intramembrane particles in the cardiac sarcolemma of normal and myopathic Syrian hamsters in a search for a morphological marker of a putative membrane defect. Hereditary cardiomyopathy in hamsters is manifested by progressive multifocal skeletal and cardiac muscle necrosis. Although pharmacological and biochemical data suggest a molecular defect in the cardiac sarcolemma, there has been no morphological observation that would substantiate this suggestion. We quantified numerical densities of intramembrane particles in freeze-fractured sarcolemmal membrane protoplasmic and extracellular faces from the left and right ventricular myocardium of female 25-day-old hamsters of the U.M.-X 7.1 cardiomyopathic line compared with sex- and age-matched randomly bred Syrian hamsters. Intramembrane particle numerical densities significantly increased above control values in cardiomyopathic hamsters for protoplasmic face (from 2188 +/- 61 to 2454 +/- 89 microns-2 in left ventricle (P less than 0.025) and from 2255 +/- 83 to 2574 +/- 56 microns-2 in right ventricle (P less than 0.001]. There was no significant difference between intramembrane particle densities of normal and cardiomyopathic hamsters for extracellular face (707 +/- 45 and 687 +/- 49 microns-2 in the left ventricle and 742 +/- 41 and 746 +/- 28 microns-2 in the right ventricle). These results implicate an increase of protoplasmic face-associated integral proteins in the sarcolemmal membrane of cardiomyopathic hamster. The significance of this finding is not known. It may represent an adaptive change related to a molecular defect in the sarcolemmal membrane of cardiomyopathic hamster.
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000235:genetics / Q000473:pathology*; D006224:Cricetinae; D005260:Female; D005614:Freeze Fracturing; D006352:Heart Ventricles / Q000473:pathology; D002479:Inclusion Bodies / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000378:metabolism; D008647:Mesocricetus; D008854:Microscopy, Electron; D012508:Sarcolemma / Q000648:ultrastructure*
chemical_list: D008565:Membrane Proteins