The Endothelin Receptor Antagonist Macitentan Improves Isosorbide-5-Mononitrate (ISMN) and Isosorbide Dinitrate (ISDN) Induced Endothelial Dysfunction, Oxidative Stress, and Vascular Inflammation

Figure 3

Pilot studies on the effective ISDN dose and administration protocol. Effects of 3 ISDN doses (10, 25, and 50 mg/kg/d) on endothelial function of rat aortic ring segments were tested by endothelium-dependent relaxation (ACh, a). Impact of the ISDN dose on endothelium-independent relaxation (ISDN) was determined by isometric tension studies in rat aortic ring segments in order to measure nitrate tolerance (b). Sensitivity to ET-1-dependent vasoconstriction was measured by increases in tone of rat aortic ring segments in response to cumulative concentrations of ET-1 (c). ISDN dose-dependent increase in the nitrosative stress marker nitrosyl-iron hemoglobin (HbNO) in whole blood of treated rats was measured by EPR spectroscopy quantification of the characteristic triplet signal (see representative spectra) (d). ISMN (75 mg/kg/d) and ISDN (25 mg/kg/d) treatment increases HbNO in whole blood of treated mice, which is decreased by macitentan therapy (quantification of the left peak of the triplet signal, see representative spectra) (e). The data are mean ± SEM from 9-12 (a, b), 6-8 (c), 5-6 (d), and 3-4 (e) independent experiments. vs. solvent control; vs. 10 mg/kg/d ISDN group; vs. 75 mg/kg/d ISMN group.

(a)

(b)

(c)

(d)

(e)