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Figure 4 Endothelium-dependent coronary vasodilation before and after coronary ischemia/reperfusion (I/R) injury in dogs in vivo. Coronary I/R significantly impaired coronary vasodilation to acetylcholine under control conditions (C) and L-NMMA (L) further suppressed the vasodilation, whereas hydroxyfasudil (HF) completely preserved the responses. The vasoconstriction induced by L-NMMA after I/R was significantly improved by hydroxyfasudil in small arteries. Hydroxyfasudil also prevented the decrease in coronary blood flow (CBF) after I/R, which effect was attenuated by L-NMMA. Number of vessels per animals used was 7/6 for control (mean diameter 120 ± 7 µm), 5/4 for L-NMMA (123 ± 8 µm), 6/4 for hydroxyfasudil (118 ± 8 µm), and 5/4 for hydroxyfasudil plus L-NMMA (125 ± 9 µm) in small arteries, and 12/6 for control (70 ± 6 µm), 8/4 for L-NMMA (69 ± 7 µm), 8/5 for hydroxyfasudil (68 ± 7 µm), and 11/6 for hydroxyfasudil plus L-NMMA (71 ± 5 µm) in arterioles. I/R = ischemia/reperfusion; B = before acetylcholine; A = after acetylcholine. *p < 0.05; **p < 0.01.