We hypothesized that nitric oxide (NO), in addition to β-adrenergic effects, may contribute to exercise-induced coronary responses after α-adrenergic receptor blockade. Data were analyzed as relationships between coronary sinus (CS) O2 saturation (CS O2sat) or coronary blood flow (CBF) and myocardial O2 consumption (MV˙o 2). As MV˙o 2 increased, CS O2sat fell more ( P < 0.05) after N ω-nitro-l-arginine methyl ester (l-NAME; slope = −2.9 ± 0.4 × 10−2 %saturation · μl O2 · min−1 · g−1) than before (slope = −2.1 ± 0.3 × 10−2%saturation · μl O2 · min−1 · g−1). The slope of CBF versus MV˙o 2 was not altered. After blockade of α-adrenergic receptors alone (phentolamine), CS O2sat failed to decrease as MV˙o 2 increased (slope = −0.1 ± 0.5 × 10−2 %saturation · μl O2 · min−1 · g−1).l-NAME given after phentolamine led to substantial decreases in CS O2sat ( P < 0.01) as MV˙o 2 increased (slope = −2.1 ± 0.4 × 10−2 percent saturation · μl O2 −1 · min−1 · g−1). CBF responses to exercise were smaller ( P < 0.01) after phentolamine + l-NAME (slope = 6.1 ± 0.1 × 10−3 ml/μl O2) than after phentolamine alone (slope = 6.9 ± 0.2 × 10−3 ml/μl O2). Thus a significant portion of exercise-induced coronary responses after α-adrenergic receptor blockade involves NO formation.
The effects of β1 and β1+2 adrenergic receptor blockade on the exercise-induced mobilization and ex vivo expansion of virus-specific T cells: implications for cellular therapy and the anti-viral immune effects of exercise