Catecholamines can induce adenosine receptor-mediated protection of the myocardium but do not participate in ischemic preconditioning in the rabbit.

Abstract

The role of catecholamines in ischemic preconditioning is unclear. Accordingly, the effects of tyramine-induced norepinephrine release and alpha 1-receptor blockade were examined. Ischemic preconditioning with a 5-minute coronary occlusion 10 minutes before a 30-minute ischemic interval resulted in only 7.7 +/- 3.1% infarction of the risk area, significantly less than that in control rabbits with isolated 30-minute coronary occlusions (34.4 +/- 3.2%, P < .01). Intravenous infusion of tyramine 10 minutes before 30 minutes of ischemia also protected the heart from infarction to an extent similar to that seen with ischemic preconditioning (6.9 +/- 2.4% infarction). This protection observed with tyramine infusion was eliminated by alpha 1-receptor blockade with BE 2254 (36.8 +/- 2.6% infarction) but was unaffected by beta-blockade with propranolol (10.5 +/- 2.4% infarction). Furthermore, the protection was unaffected when the tyramine-induced hypertension was attenuated by allowing blood to flow into a volume reservoir (3.9 +/- 0.8% infarction, P < .01 vs control value). The nonselective adenosine-receptor blocker PD 115,199 also eliminated tyramine-induced protection (40.2 +/- 5.6% infarction), indicating that adenosine is involved in adrenergic-mediated protection. BE 2254 could not block ischemic preconditioning (3.9 +/- 1.1% infarction, P < .01 vs control value). Therefore, catecholamine release before prolonged ischemia can protect the heart from infarction via the alpha 1-receptor, but adenosine receptor stimulation is also involved. alpha-Adrenergic stimulation does not appear to be critical to the protection observed after ischemic preconditioning.

• Authors: J D Thornton, J F Daly, M V Cohen, X M Yang, J M Downey
• Journal: Circulation research (Circ Res) Vol. 73 Issue 4 Pg. 649-55 (Oct 1993) ISSN: 0009-7330 [Print] United States
• PMID: 8396502 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Catecholamines
• Receptors, Adrenergic, alpha
• Receptors, Purinergic
• Adenosine
• Tyramine

Topics

• Adenosine (physiology)
• Animals
• Catecholamines (physiology)
• Female
• Male
• Myocardial Ischemia (physiopathology)
• Rabbits
• Rats
• Receptors, Adrenergic, alpha (physiology)
• Receptors, Purinergic (physiology)
• Species Specificity
• Tyramine (pharmacology)