Myocardial oxygen consumption modulates adenosine formation by canine right ventricle in absence of hypoxia

Myocardial adenosine formation varies with myocardial oxygen consumption (M VO2), but whether concurrent hypoxia is required for adenosine formation is uncertain. Changes in right coronary (RC) perfusion pressure (RCP) produce directionally similar alterations in right ventricular (RV) MVO2 and in RC venous Po-2 (P(v)o(2)), an index of myocardial Po-2. RCP was varied in 10 anesthetized, open chest dogs to determine if, under these conditions. RV f ormation of adenosine would increase with MVO2 in absence of myocardial hyp oxia. Dialysis probes were implanted in the mid myocardium of RV free wall for collecting dialysate samples for HPLC analyses to estimate interstitial adenosine and other purines. Coronary venous blood was sampled from a supe rficial vein draining the RC artery (RCA) perfusion territory. At 115+/-3 m mHg baseline RCP, RC blood Row (RCBF) = 0.51 +/- 0.04 ml/min/g, MVO2 = 4.6 +/- 0.5 ml/min/100g, P(v)o(2) = 34 +/- 1.5 mmHg, and dialysate adenosine = 0.27 +/- 0.03 mu M When RCP was lowered to 61 +/- 1 mmHg by adjusting an oc cluder on the proximal RCA, RCBF decreased to 0.36 +/- 0.03 ml/min/g, MVO2 fell to 3.7 +/- 0.4 ml/min/100 g, lactate uptake remained positive, P(v)o(2 ) Fell to 30 +/- 1.7 mmHg, and dialysate adenosine decreased to 0.20 +/- 0. 03 mu M. Reactive hyperemia of 1.25 +/- 0.13 ml/ min/g was observed when th e RCA constriction was released, although dialysate adenosine had fallen. W hen RCP was elevated to 164 +/- 2 mmHg by inflating a balloon catheter in t he descending aorta, RCBF increased to 0.70 +/- 0.06 ml/min/g, MVO2 increas ed to 5.8 +/- 1.0 ml/min/100 g, P(v)o(2) rose to 39 +/- 2.3 mmHg, and dialy sate adenosine increased to 0.33 +/- 0.04 mu M. These data indicate that (1 ) RV oxygen demand varies with RCP; (2) if RV ischemia is absent, myocardia l adenosine formation is modulated by MVO2, with Ilo requirement for hypoxi a; (3) pressure-flow antoregulation is relatively ineffective in the RC cir culation, where adenosine does not mediate and may even blunt autoregulatio n. (C) 2000 Academic Press.