title: alpha 2-Adrenergic receptor binding in canine Purkinje fibers.
abstract: Autoradiograms were developed from free running strands of Purkinje fibers and from left ventricular myocardium of dog hearts exposed to [7-methoxy-3H]prazosin or [O-methyl-3H]yohimbine in the presence or absence of excessive non-radioactive ligands. Both Purkinje fiber and ventricular myocardium show high density, tissue-specific binding to [3H]prazosin. In contrast, high density, tissue-specific binding to [3H]yohimbine was present in Purkinje fibers but not in ventricular myocardium. Membrane fractions showed high affinity, saturable, and displaceable binding with [3H]yohimbine in preparations from canine cardiac Purkinje fibers but not those from canine cardiac ventricular myocardium. Scatchard analysis of the canine Purkinje membrane alpha 2-adrenergic receptor binding showed a Bmax of 54.9 fmol/mg protein with a Kd of 6.25 nM. These results confirm the electrophysiological findings that post-junctional alpha 2-adrenergic receptors are present in Purkinje fibers.
authors.affiliation: Cardiovascular Division, Department of Internal Medicine, University of Iowa, College of Medicine, Iowa City, 52242, USA.
authors.forename: H C
authors.initials: HC
authors.lastname: Lee
authors.forename: R A
authors.initials: RA
authors.lastname: Samson
authors.forename: J J
authors.initials: JJ
authors.lastname: Cai
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000378:metabolism; D000818:Animals; D004285:Dogs; D005260:Female; D006352:Heart Ventricles; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D011224:Prazosin / Q000378:metabolism; D011690:Purkinje Fibers / Q000378:metabolism*; D011869:Radioligand Assay; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D015016:Yohimbine / Q000378:metabolism
chemical_list: D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D015016:Yohimbine; D011224:Prazosin