DIFFERENTIAL REGIONAL RESPONSES OF MYOCARDIAL INTERSTITIAL NORADRENALINE LEVELS TO CORONARY-OCCLUSION

Objective: The aim was to investigate the influence of coronary occlusion on myocardial interstitial noradrenaline levels in the ischaemic and non-ischaemic regions, using the dialysis technique. Methods: In nine anaesthetised cats, regional ischaemia was produced by occlusion of the left anterior descending coronary artery for 90 min. Using the dialysis technique, dialysates were sampled from both the ischaemic region and the non-ischaemic left circumflex coronary artery region. Dialysate noradrenaline concentrations, as an index of myocardial interstitial noradrenaline content, were measured by high performance liquid chromatography. Myocardial blood flows in the ischaemic and non-ischaemic regions were measured by the hydrogen clearance method. Results: In the non-ischaemic region, neither myocardial blood flow nor dialysate noradrenaline concentration showed significant change. In the ischaemic region, myocardial blood flow decreased significantly, from 117(SEM 12) at control to 23(3) ml.min-1.100 g-1, and dialysate noradrenaline concentration increased significantly, from 56.8(4.5) pg.ml-1 at control to 528.8(155.4) pg.ml-1 at 0-30 min of occlusion, 4212.0(1447.7) pg.ml-1 at 30-60 min, and 4179.8(1668.5) pg.ml-1 at 60-90 min. At 0-30 min of the reperfusion period, dialysate noradrenaline concentration in the postischaemic region decreased significantly to 420.2(152. 1) pg.ml-1. Conclusions: Coronary occlusion increased myocardial interstitial noradrenaline levels in the ischaemic region, but not in the non-ischaemic region.