ADRENERGIC INFLUENCES ON CARDIAC-FUNCTION DURING VENTRICULAR-FIBRILLATION IN ISOLATED RAT HEARTS

Effects of norepinephrine (NE, 10(-6) M), epinephrine (E, 10(-6) M), and vehicle on coronary blood flow (CF), oxygen consumption, and lactate release were compared in 32 isolated rat hearts during 5 min of ventricular fibrillation (VF). After VF, tissue concentrations of ATP, AMP, creatinine phosphate (CP), and lactate were measured. Perfusion of treatments started 30 s after onset of VF and was maintained throughout VF. CF during VF was greater (P < 0.005) during perfusion of E (mean +/- SE, 5.73 +/- 0.15 ml/min) than NE (5.06 +/- 0.32 ml/min) or vehicle (5.11 +/- 0.18 ml/min). Oxygen consumption during VF was higher during perfusion of E (29.5 +/- 0.9-mu-l.min-1.g wet heart wt-1) than vehicle (27.3 +/- 0.7-mu-l.min-1.g-1; P < 0.05); average oxygen consumption during NE (27.6 +/- 1.4-mu-l.min-1.g-1) and vehicle were comparable. After NE, but not E, tissue AMP concentrations were significantly increased, and CP concentrations were reduced compared with vehicle (P < 0.05). Enhanced consumption of high-energy phosphates during NE suggests that there is also an enhanced demand for oxygen. However, unlike during E, during NE this demand is not met by an augmented CF. Thus, compared with E, NE treatment during VF may increase the risk of hypoxic damage.