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Figure 2 Effect of dobutamine (dob) and saline on the rate–pressure product (rpp). *p < 0.05 vs. baseline (bl) for dobutamine 20, 30, and 40 µg/kg per min in groups 1, 3, 4, and 6; for dobutamine 30 and 40 µg/kg per min in group 5; and for isdn in group 1. p < 0.05 vs. preceding value in groups 1, 3, 4, 5, and 6. white boxes represent group 1 (normal coronary arteries); white circles = group 2 (normal coronary arteries, but dobutamine replaced by saline); blue diamonds = group 3 (mildly atherosclerotic coronary arteries); black triangles = group 4 (stenotic coronary arteries); white triangles = group 5 (stenotic coronary arteries, pretreated with phentolamine); blue triangles = group 6 (stenotic coronary arteries, pretreated with L-arginine).