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Figure 1. Increased vascular dysfunction, fibrosis, and stiffness in LCR rats with aging. The contractile force in mesenteric artery rings of young (4-month old) and aged (27-month old) LCR and HCR rats in response to phenylephrine (PE) was measured by wire myography (mean ± SEM; n = 5) (A). Concentration-response curves for acetylcholine (ACH) induced relaxation of mesenteric arteries from young (B) and old age (C) LCR and HCR rats (mean ± SEM; n = 5). Half-maximum relaxation concentration of ACH [-log(EC50)] was calculated from independent dose-response curves and plotted as mean ± SEM, n = 5 (D). Representative Western blot of eNOS protein expression in aortic lysates. Densitometry analysis of eNOS protein levels normalized to β-tubulin levels (mean ± SEM, n = 3) (E). Representative fluorescence images of aortic cross sections stained for immunoreactive total eNOS (red) or phospho-eNOS Ser1177 (green). Data are presented as mean integrated density/ROI ± SEM where n = 4 [(F), scale = 50 μm)]. Pressure vs strain data of thoracic aorta segments from young (G) and old (H) LCR and HCR rats were analyzed using pressure myography. The relative stiffness coefficient (H) was calculated by fitting pressure vs strain data to an exponential formula (mean ± SEM, n = 5) (I). Representative images of rat aortic cross sections stained with Picrosirius red (PSR) (J). Representative fluorescence images of aortic cross sections co-stained for TGF-β (red) and SM-α-actin (green). Bright yellow fluorescence indicates colocalization of TGF-β and SM-α-actin. Data are presented as mean integrated density/ROI ± SEM where n = 4 (K). *P < 0.05; **P < 0.01; ****P < 0.0001.