title: Beta-adrenoceptor density in chronic infarcted myocardium: a subtype specific decrease of beta1-adrenoceptor density.
abstract: Beta-adrenoceptor density is altered in different cardiac diseases. In heart failure beta-adrenoceptor density is down regulated but in acute myocardial ischemia beta-adrenoceptor density is up regulated. In hearts with myocardial infarction total beta-adrenoceptor density is decreased shortly after myocardial infarction.
  
  
  OBJECTIVE
  To investigate whether total beta-adrenoceptor number is altered in the chronic phase after myocardial infarction, and to identify the specificity of alteration, we studied male Wistar rats (n = 18) which underwent a ligation of the left coronary artery or a sham operation. Twelve weeks after coronary ligation, rats were sacrificed and hearts were excised, perfused to obtain blood-free myocardium and frozen in liquid nitrogen. Infarcted myocardium was identified visually and separated from non-infarcted myocardium. Total beta-adrenoceptor number was calculated in fmol (-)-[125I]iodocyanopindolol specifically bound/mg protein and the relative amount of beta1- and beta2-adrenoceptor density was measured by inhibition of (-)-[125I]iodocyanopindolol binding with CGP 20712 A.
  
  
  RESULTS
  Total beta-adrenoceptor number in infarcted myocardium was significantly decreased (25.7+/-1.4 vs. 24.9+/-2.2 vs. 20.1+/-3.2 fmol/mg protein (P=0.03) resp. Sham vs. Non-infarcted vs. Infarcted myocardium), due to a decrease of only beta1-adrenoceptor density (14.7+/-0.61 vs. 12.7+/-1.09 vs. 4.84+/-0.96 fmol/mg protein (P=0.004) resp.), whereas the beta2-adrenoceptor density and the dissociation constant (Kd) were not significantly decreased.
  
  
  CONCLUSIONS
  In the infarcted myocardium total beta-adrenoceptor density is decreased due to a decreased beta1-adrenoceptor density at 12 weeks after myocardial infarction.
authors.affiliation: Department of Clinical Pharmacology, University of Groningen, The Netherlands.
authors.forename: R L
authors.initials: RL
authors.lastname: Anthonio
authors.forename: O E
authors.initials: OE
authors.lastname: Brodde
authors.forename: D J
authors.initials: DJ
authors.lastname: van Veldhuisen
authors.forename: E
authors.initials: E
authors.lastname: Scholtens
authors.forename: H J
authors.initials: HJ
authors.lastname: Crijns
authors.forename: W H
authors.initials: WH
authors.lastname: van Gilst
mesh_terms: D000818:Animals; D002908:Chronic Disease; D015536:Down-Regulation; D006439:Hemodynamics; D008297:Male; D009203:Myocardial Infarction / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*
chemical_list: D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2