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Figure 1 Typical recording obtained from two segments of a human internal mammary artery. Several concentration-response curves for phenylephrine (PE) were conducted at 60-min intervals. Upper panel: Angiotensin II was added to the bath of the artery 10 min before the last concentration-response curves for PE. Lower panel: The solvent only (physiologic salt solution) was added. The potentiating effect of angiotensin II was calculated by comparing the second concentration-response curve (2) with the first (1). W = washout.