title: Comparative effects of continuous warm blood and intermittent cold blood cardioplegia on coronary reactivity.
abstract: BACKGROUND
  Cardioplegia is known to affect coronary vascular reactivity. We examined the effects of intermittent cold and continuous warm blood cardioplegia on beta-adrenoceptor-mediated, adenosine triphosphate-sensitive K+ (K+ATP)-channel-mediated, and endothelium-dependent relaxation and on the myogenic tone of coronary arterioles.
  
  
  METHODS
  Pigs were placed on cardiopulmonary bypass. Hearts were arrested for 1 hour with a cold blood cardioplegic solution administered intermittently (n = 12; iCB-CP) or with a warm blood cardioplegic solution delivered continuously (n = 12; cWB-CP). Selected hearts (n = 6 in each group) were then reperfused for 1 hour. In vitro relaxation responses of precontracted microvessels (50 to 160 microns) were studied in a pressurized no-flow state.
  
  
  RESULTS
  Relaxation in response to isoproterenol (beta-adrenergic agonist) was similar after iCB-CP and cWB-CP, whereas forskolin (adenylate cyclase activator)-induced relaxation was impaired more after iCB-CP than after cWB-CP. After reperfusion the respective responses were similar. Both iCB-CP and cWB-CP preserved receptor-mediated, endothelium-dependent relaxation in response to adenosine, 5'-diphosphate; non-receptor-mediated endothelium-dependent relaxation in response to A23187; endothelium-independent cyclic guanosine monophosphate-mediated relaxation in response to sodium nitroprusside, and K+ATP-channel-mediated relaxation. Relaxations in response to 8-bromo-cyclic guanosine monophosphate (a cyclic guanosine monophosphate-dependent protein kinase activator) and to 8-bromo-cyclic adenosine monophosphate (a cyclic adenosine monophosphate-dependent protein kinase activator) were impaired after iCB-CP alone and after reperfusion, whereas the respective responses were not affected after cWB-CP. Myogenic tone was decreased similarly after iCB-CP and cWB-CP but was not further altered after reperfusion. Cardiac function was similar after iCB-CP and cWB-CP.
  
  
  CONCLUSIONS
  These results suggest that cWB-CP is similar to iCB-CP in its ability to preserve endothelium-dependent relaxation and K+ATP-channel function. The superior preservation of beta-adrenergic-cyclic adenosine monophosphate-mediated coronary responses after cWB-CP is brief and associated with minimal improvement of myocardial function and myogenic tone.
authors.affiliation: Department of Surgery, Beth Israel-Deaconess Medical Center, Boston, MA 02215, USA.
authors.forename: M
authors.initials: M
authors.lastname: Tofukuji
authors.forename: A
authors.initials: A
authors.lastname: Stamler
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: M D
authors.initials: MD
authors.lastname: Hariawala
authors.forename: A
authors.initials: A
authors.lastname: Franklin
authors.forename: F W
authors.initials: FW
authors.lastname: Sellke
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001769:Blood; D000001:Calcimycin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology; D004789:Enzyme Activation; D006146:Guanidines / Q000494:pharmacology; D006324:Heart Arrest, Induced / Q000379:methods*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D020110:Pinacidil; D015221:Potassium Channels / Q000378:metabolism; D013552:Swine; D013696:Temperature; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D006146:Guanidines; D015221:Potassium Channels; D014665:Vasodilator Agents; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000001:Calcimycin; D000244:Adenosine Diphosphate; D020110:Pinacidil; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D007545:Isoproterenol