Role of adenosine in catecholamine-induced global coronary functional hyperemia in isolated guinea pig hearts

This study was designed to test the hypothesis that endogenous adenosine participates in the global coronary functional hyperemia accompanying intracoronary infusions of norepinephrine (NE) and isoproterenol (ISO). Intracoronary adenosine deaminase (ADA) was employed to test the hypothesis in isolated, perfused guinea pig hearts. We measured coronary perfusate flow (CPF) at a constant coronary perfusion pressure. Heart rate (HR), left ventricular pressure, and its rate of development were also measured. Global myocardial oxygen consumption (MVO₂) and oxygen extraction were calculated, and blood gases and pH were measured routinely in inflow and outflow perfusate samples. In the absence of ADA, NE and ISO increased HR 67 ± 6 and 106 ± 11 beats min^-1, left ventricular pressure development 519 ± 46 and 375 ± 35 mm Hg s^-1, MVO₂ 22 ± 2 and 28 ± 3 μl · min^-1 · g^-1, and CPF 1.6 ± 0.2 and 2.2 ± 0.2 ml min^-1 · g^-1, respectively. With constant infusion of ADA (4.5 U min^-1 · g^-1, a dose which produces no direct effects on cardiac function) for 4 min, similar increments in HR and left ventricular pressure development were achieved with both catecholamines. Corresponding changes in MVO₂ (9 ± 2 and 6 ± 3 μl · min^-1 · g^-1) were significantly less than those seen in the absence of ADA. Moreover, CPF did not increase in response to NE and ISO in the presence of ADA. These findings support an important role for adenosine in catecholamine-induced global coronary functional hyperemia in isolated, perfused guinea pig hearts.