Cytochemical localization of a "basic" ATPase to canine myocardial surface membrane.
Enzymatic properties of a canine cardiac muscle microsomal fraction were determined to localize in situ a "basic," divalent cation dependent adenosine triphosphatase (ATPase) by ultrastructural cytochemistry. The microsomal fraction had a buoyant density of 1.08--1.13 (20--30% [w/w] sucrose) and hydrolyzed adenosine triphosphate in the presence of Mg2+, Ca2+, Mn2+, or Co2+, but not in that of Sr2+ or Ni2+, under conditions that inhibited interfering (Na+ + K+)-ATPase and sarcoplasmic reticulum Ca2+-ATPase activities. "Basic" ATPase was localized in paraformaldehyde-fixed tissue in a medium containing Mg2+ or a high Ca2+ concentration (4 mM). A free Pb2+ concentration of less than 1 microM was used to capture enzymatically released phosphate anions. Electron-dense lead precipitates were present at the plasmalemma, T-system, and intercalated disc membranes with the exception of the nexus. These studies suggest that "basic" ATPase activity is associated with surface membrane structures of canine cardiac muscle.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D003896:Desmosomes / Q000201:enzymology; D004285:Dogs; D006651:Histocytochemistry; D007854:Lead / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D008861:Microsomes / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology
D007854:Lead; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium