Figure 4. Contribution of β1- and β2-AR to isoproterenol-induced vasodilation from isolated coronary arterioles. Vasorelaxation to isoproterenol, primarily a non-selective β1-, β2-, and β3-AR agonist, was significantly impaired in the O+BM group compared to O+SVF ($) (A). Isoproterenol with ICI118551, a β2-AR antagonist, eliminated differences between the groups. Compared to pre-incubation, all groups except OC (YC, O+SVF, and O+BM) had significant attenuation in the inhibited dose response (^) at several concentrations (B). Isoproterenol with CPG20712A, a β1-AR antagonist, also eliminated differences between the groups, and all groups exhibited significant attenuation in the response compared to pre-inhibition (^) (C). No group differences to isoproterenol were noted following inhibition with both ICI118551 and CPG20712A, and all groups exhibited significant attenuation in the response compared to pre-inhibition (^) at every concentration (D). P ≤ 0.05 vs Young Control (*), vs Old Control (#), vs Old+SVF, and pre- vs post-inhibition (^); data are presented as means±SEM and analyzed with two-way repeated measures ANOVA, paired for inhibitor analysis, followed by post-hoc Bonferroni test.