title: Acute depression of myocardial beta-adrenergic receptor signaling during cardiopulmonary bypass: impairment of the adenylyl cyclase moiety. Duke Heart Center Perioperative Desensitization Group.
abstract: BACKGROUND
  Previously the authors showed that myocardial beta-adrenergic (betaAR) function is reduced after cardiopulmonary bypass (CPB) in a canine model Whether CPB results in similar effects on betaAR function in adult humans is not known. Therefore the current study tested two hypotheses: (1) That myocardial betaAR signaling is reduced in adult humans after CPB, and (2) that administration of long-term preoperative betaAR antagonists prevents this process.
  
  
  METHODS
  After they gave informed consent, 52 patients undergoing aortocoronary surgery were enrolled. Atrial biopsies were obtained before CPB and immediately before discontinuation of CPB. Plasma catecholamine concentrations, myocardial betaAR density, and functional responsiveness (basal, isoproterenol, zinterol, sodium fluoride, and manganese-stimulated adenylyl cyclase activity) were assessed.
  
  
  RESULTS
  Catecholamine levels increased significantly during CPB (P < 0.005). Myocardial betaAR adenylyl cyclase coupling decreased during CPB, as evidenced by a 21% decrease in isoproterenol-stimulated adenylyl cyclase activity (750 [430] pmol cyclic adenosine monophosphate per milligram total protein 15 min before CPB compared with 540 [390] at the end of CPB, P = 0.0062, medians [interquartile range]) despite constant betaAR density. Differential activation along the betaAR signal transduction cascade localized the defect to the adenylyl cyclase moiety. Administration of long-term preoperative betaAR antagonists did not prevent acute CPB-induced myocardial betaAR dysfunction.
  
  
  CONCLUSIONS
  These data indicate that the myocardial adenylyl cyclase response to betaAR agonists decreases acutely in adults during aortocoronary surgery requiring CPB, regardless of whether long-term preoperative betaAR antagonists are administered. The mechanism underlying acute betaAR dysfunction appears to be direct impairment of the adenylyl cyclase moiety. Similar increases in manganese-stimulated activity before and at the end of CPB show preserved adenylyl cyclase catalytic activity, suggesting that other mechanisms (such as decreased protein levels or altered isoform expression or function) may be responsible for decreased adenylyl cyclase function.
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: J V
authors.initials: JV
authors.lastname: Booth
authors.forename: K P
authors.initials: KP
authors.lastname: Landolfo
authors.forename: L C
authors.initials: LC
authors.lastname: Chesnut
authors.forename: E
authors.initials: E
authors.lastname: Bennett-Guerrero
authors.forename: M A
authors.initials: MA
authors.lastname: Gerhardt
authors.forename: D M
authors.initials: DM
authors.lastname: Atwell
authors.forename: H E
authors.initials: HE
authors.lastname: El-Moalem
authors.forename: M S
authors.initials: MS
authors.lastname: Smith
authors.forename: B L
authors.initials: BL
authors.lastname: Funk
authors.forename: C M
authors.initials: CM
authors.lastname: Kuhn
authors.forename: M M
authors.initials: MM
authors.lastname: Kwatra
authors.forename: D A
authors.initials: DA
authors.lastname: Schwinn
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D002315:Cardiopulmonary Bypass; D002395:Catecholamines / Q000097:blood; D005260:Female; D006321:Heart / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D011943:Receptors, Adrenergic, beta; D000262:Adenylyl Cyclases