Dj. Duncker et al., ROLE OF ADENOSINE IN THE REGULATION OF CORONARY BLOOD-FLOW IN SWINE AT REST AND DURING TREADMILL EXERCISE, American journal of physiology. Heart and circulatory physiology, 44(5), 1998, pp. 1663-1672
A pivotal role for adenosine in the regulation of coronary blood flow
is still controversial. Consequently, we investigated its role in the
regulation of coronary vasomotor tone in swine at rest and during grad
ed treadmill exercise. During exercise, myocardial O-2 consumption inc
reased from 167 +/- 18 mu mol/min at rest to 399 +/- 27 mu mol/min at
5 km/h (P less than or equal to 0.05), which was paralleled by an incr
ease in O-2 delivery, so that myocardial O-2 extraction (76 +/- 1 and
78 +/- 1% at rest and 5 km/h, respectively) and coronary venous Po-2 (
24.5 +/- 1.0 and 22.8 +/- 0.3 mmHg at rest and 5 km/h, respectively) r
emained unchanged. After adenosine receptor blockade with 8-phenyltheo
phylline (5 mg/kg iv), the relation between myocardial O-2 consumption
and coronary vascular resistance was shifted toward higher resistance
, whereas myocardial O-2 extraction rose to 81 +/- 1 and 83 +/- 1% at
rest and 5 km/h and coronary venous Po-2 fell to 19.2 +/- 0.8 and 18.9
+/- 0.8 mmHg at rest and 5 km/h, respectively (all P less than or equ
al to 0.05). Thus, although adenosine is not mandatory for the exercis
e-induced coronary vasodilation, it exerts a vasodilator influence on
the coronary resistance vessels in swine at rest and during exercise.