Beta-adrenergic receptors and enzymes in rat myocardial membranes: implications of fractionation procedures and beta-adrenoceptor antagonists.
1. We performed an enzymatic characterization of two different fractionation procedures of ventricles from rat hearts. The enzymatic assays covered succinic dehydrogenase as a marker for inner mitochondrial membranes, monoamine oxidase as a marker for outer mitochondrial membranes, NADPH-cytochrome c reductase and RNA as endoplasmatic reticular markers, acid phosphatase as a lysosomal marker, and lactic dehydrogenase as a marker for the "soluble" compartment; DNA was estimated for nuclear contamination. 2. The plasma membrane markers 5'-nucleotidase, Ca2+-ATPase, Mg2+-ATPase, Na+-K+-ATPase, and adenylate cyclase were determined. 3. The roughly prepared membrane fractions showed increased yields of the membrane markers; the number of beta receptors, determined with (-)-[3H] dihydroalprenolol and DL-propranolol, amounted to 68 +/- 6 fmol/mg protein (KD = 3390 +/- 450 pmol, Hill coefficient = 1.5). 4. The membrane fraction prepared with a linear sucrose gradient showed an increased inner mitochondrial membrane marker; presumably the outer mitochondrial membrane was stripped off. The beta-receptor number was 39 +/- 3 fmol/mg protein (KD = 6250 +/- 300 pmol; Hill coefficient = 1.2).
Schrader
E
E
Department of Pharmacology, University of Regensburg, Germany.
Inczédy-Marcsek
M
M
Grobecker
H
H
D000818:Animals; D002462:Cell Membrane / Q000032:analysis; D004082:Dihydroalprenolol / Q000378:metabolism; D006352:Heart Ventricles / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D007700:Kinetics; D008297:Male; D008854:Microscopy, Electron; D011433:Propranolol / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D013347:Subcellular Fractions / Q000032:analysis*
D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D011433:Propranolol