Abstract P300: A Novel Highly Selective Adenosine A 1 Receptor Agonist (VCP28) Reduces Ischemia/Reperfusion Injury at Concentrations that Do Not Affect Heart Rate

Abstract

Whilst adenosine A1 receptor agonists have repeatedly been shown to protect the ischaemic myocardium, the clinical use of these agents is limited by strong cardiodepressant effects. The cardioprotective effects of a novel adenosine A1 receptor agonist N6-(2,2,5,5-tetramethylpyrrolidin-1-yloxyl-3-ylmethyl) adenosine (VCP28) were compared with the selective adenosine A1receptor agonist N6-cyclopentyladenosine (CPA) in a H9c2(2–1) cardiac cell line-simulated ischemia (SI) model (12 hours) and a global ischemia (30 minutes) and reperfusion (60 minutes) model in isolated rat heart model. H9c2(2–1) cells were treated with CPA and VCP28 at the start of ischemia for entire ischemic duration, whereas isolated rat hearts were treated at the onset of reperfusion for 15 minutes. In a H9c2(2–1) cell SI model, CPA and VCP28 (100 nM) significantly (P , 0.05, n = 5–6) reduced the proportion of nonviable cells (30.88% 6 2.49% and 16.17% 6 3.77% of SI group, respectively) and lactate dehydrogenase efflux. In isolated rat hearts, CPA and VCP28 significantly (n = 6–8, P , 0.05) improved postischemic contractility (dP/dtmax, 81.69% 6 10.96%, 91.07% 6 19.87% of baseline, respectively), left ventricular developed pressure, and end diastolic pressure and reduced infarct size. The adenosine A1 receptor antagonist DPCPX abolished the cardioprotective effects of CPA and VCP28 in both models. At the concentrations used in the ischaemia models, VCP28 had no effect on heart rate, unlike CPA. In conclusion, the adenosine A1 receptor agonist VCP28 has cardioprotective equal effects to the prototype A1 agonist CPA at concentrations that have no effect on heart rate.