Figure 3.

Enhanced myocardial perfusion during stress following exercise training requires Kvβ2 proteins. (A) Exemplary B-mode and nonlinear contrast images (before and during contrast agent infusion). (B) Representative replenishment plots showing time course and magnitude of contrast intensity following destruction phase in sedentary and exercise-trained mice at rest (baseline) and stress (dobutamine, 10 μg/kg/min, i.v.). Data are fit with a one-phase exponential growth function: Y = A(1-e^βx). (C) Summary plot of myocardial perfusion at rest and during dobutamine-induced stress in sedentary and exercise-trained mice. **p < 0.01, ns: p > 0.05, paired t-test. N = 5–6 mice. (D) Relationships between myocardial perfusion and HR in anesthetized sedentary and exercise-trained mice at rest and stress. **p < 0.01, mixed effects analysis on perfusion: HR, n = 5–6 mice. (E) Representative proximity ligation images showing positive sites of interaction (red) between Kv1.5 and Kvβ1, and Kv1.5 and Kvβ2 in coronary arterial smooth muscle cells from sedentary and exercised mice. Singly labelled cells for Kv1.5 are shown as a control. DAPI nuclear stain is shown in blue. Scale bars represent 10 μm. (F) Summary plot showing the number of PLA-positive sites/μm² of cell footprint area in coronary arterial smooth muscle cells from sedentary and exercise-trained mice labelled for Kv1.5 alone, Kv1.5 and Kvβ1, and Kv1.5 and Kvβ2. *p < 0.05, ns: p > 0.05, Mann Whitney test. (G) Relationships between myocardial perfusion and HR in sedentary and exercise-trained β2^−/− mice at rest and stress. p > 0.05, mixed effects analysis on perfusion:HR, n = 5–6 mice. (H) Relationships between myocardial perfusion and HR in sedentary and exercise-trained rtTA and rtTA:Kcnab1 mice at rest. *p < 0.05, one-way ANOVA with Dunnett's multiple comparisons test on perfusion:HR, n = 5–6 mice.