Norepinephrine-induced delayed cardioprotection against stunning is at the expense of a higher postischemic arrhythmia rate.
OBJECTIVE
alpha(1)-adrenoceptor activation confers myocardial protection from ischemic injury. We tested whether norepinephrine mediates delayed cardioprotection against stunning and whether this alters postischemic arrhythmias.


METHODS
New Zealand White rabbits were assigned to three groups: Control-group (n=7): no drugs. Norepinephrine-group (n=7): 75 microg norepinephrine/kg bodyweight (bw). Norepinephrine/prazosin-group (n=7):75 microg norepinephrine and 15 microg prazosin/kg bw. After 24 h, hearts were excised, perfused with buffer and subjected to 20 min of ischemia followed by 120 min of reperfusion.


RESULTS
(a) Developed pressures (dP) (P(syst)-P(diast)) at the end of reperfusion: C: 51.2+/-5.0%, NE: 71.7+/-5.1% (p<0.05 vs. C), NEP: 50.7+/-5.0%. (b) Ventricular extra beats (vebs) were detected throughout the experiments. C: 0.41+/-0.15 vebs/min, NE: 1.06+/-0.18 vebs/min (p<0.05 vs. C), NEP: 1.17+/-0.3 vebs/min.


CONCLUSIONS
Norepinephrine confers delayed preconditioning against myocardial stunning via an alpha(1)-adrenoceptor mediated pathway. Norepinephrine-mediated preconditioning involves a beneficial effect towards stunning, but at the expense of a higher rate of postischemic ventricular arrhythmia.
Marktanner
Ralph
R
Department of Thoracic and Cardiovascular Surgery, Heinrich-Heine-University Düsseldorf, Germany. marktann@uni-duesseldorf.de
Nacke
Peter
P
Feindt
Peter
P
Hohlfeld
Thomas
T
Gams
Emmeran
E
D000316:Adrenergic alpha-Agonists / Q000009:adverse effects / Q000627:therapeutic use*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced*; D003326:Coronary Circulation / Q000187:drug effects; D003402:Creatine Kinase / Q000378:metabolism; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D017682:Myocardial Stunning / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology; D009638:Norepinephrine / Q000009:adverse effects / Q000627:therapeutic use*; D009924:Organ Culture Techniques; D011817:Rabbits; D014662:Vasoconstrictor Agents / Q000009:adverse effects / Q000627:therapeutic use
D000316:Adrenergic alpha-Agonists; D014662:Vasoconstrictor Agents; D003402:Creatine Kinase; D009638:Norepinephrine