Figure 5.

Number of resistance vessels and relative dilatory responses to endothelium-dependent stimulation in ischemic myocardium. Synchrotron radiation microangiography was performed to evaluate vessel number and caliber and relative dilatory responses to acetylcholine and dobutamine hydrochloride in resistance vessels (control: n = 11, combined: n = 11, cell-sheet: n = 5, OM: n = 6). Using iodinated agents, coronary microcirculation in ischemic areas was clearly visualized in anesthetized closed-chest rats. Representative angiogram frames for all treatment groups at baseline, and in response to acetylcholine and dobutamine hydrochloride (a). Yellow and red asterisks indicate vessels showing dilation and constriction in response to acetylcholine and dobutamine hydrochloride, respectively. Quantitative analyses of (b) vessel internal diameter and (c) visible vessel number at baseline according to branching order. Vessel internal diameter at baseline (before agent administration) tended to decrease according to branching order and differed among the groups with larger first branching order arteries observed in the combined group (b). Moreover, the combined group had a greater number of third and fourth branching order arterial vessels (resistance arterial vessels) at baseline (c). Mean caliber changes in response to (d) acetylcholine and (e) dobutamine hydrochloride. Acetylcholine-mediated dilation in the third and fourth branching orders was significantly different among the groups. The mean caliber changes in response to acetylcholine in the combined group were 28 ± 8% and 32 ± 8% for the third and fourth order branches respectively, which were greater than in the others (d). Similarly, the mean caliber changes in response to dobutamine hydrochloride in the combined group were 31 ± 7% and 34 ± 7%, respectively, which were greater than in the others (e).