show calculated densitometric ratios of pMYPT1/MYPT1 and pMLC/MLC
show calculated densitometric ratios of pMYPT1/MYPT1 and pMLC/MLC. pulmonary vasodilatory activity, which could contribute to their long-term beneficial effect against pulmonary hypertension. Vascular smooth muscle relaxation mediated via activation of myosin light chain phosphatase (Ca2+ desensitization) appears to play a role in the imatinib-induced pulmonary vasodilation. test, repeated measure ANOVA, or ANOVA with Scheffe’s post hoc test for multiple comparisons. Differences were considered significant at 0.05. Results Effects of Imatinib on Agonist-Induced Contractions in Pulmonary Arterial Rings Imatinib concentration-dependently reversed serotonin-induced (Figure 1A) and U46619-induced (Figure 1B) contractions in pulmonary arterial rings isolated from normal rats. These relaxations were not reduced by endothelial removal (Figures 1A and 1B). Open in a separate window Figure 1. Concentration-relaxation curves to imatinib in endothelium-intact (= 4 in each group). Effects of Imatinib on MLCP Activity and MLC Phosphorylation MLCP activity Rabbit polyclonal to TrkB and MLC phosphorylation were measured as indices for Ca2+ sensitivity and smooth muscle contractility, respectively. In agreement with previous studies (19), U46619 increased MLCP activity (as reflected by an increase in phosphorylation of its regulatory subunit MYPT1 at Thr850) (Figure 2A) as well as the phosphorylation of MLC (Figure 2B) in pulmonary arterial rings from normal rats. Imatinib (30 M) significantly reduced the U46619-induced increased phosphorylation of MYPT1Thr850 and MLC. Open in a separate window Figure 2. Effects of imatinib (30 M) on U46619-induced increase in phosphorylation of the regulatory subunit of (show representative immunoblots for phosphorylated (p) and total MYPT1 and MLC. show calculated densitometric ratios of pMYPT1/MYPT1 and pMLC/MLC. Values are means SE (= 5C6 in each group) normalized to the ratio for controls (without U46619 and imatinib) as a value of 1 1. * 0.05. Effects of Various TKIs on Contractions in Pulmonary Arterial Rings Three different TKIsimatinib, nilotinib, and sorafenibreversed U46619-induced contractions in endothelium-intact pulmonary arterial rings from normal rats pretreated with l-NNA (Figure 3A). All SU5416/hypoxia/normoxia-exposed rats developed severe PH (RV/LV+S ratio, 0.64 0.03 [= 9] versus 0.20 0.02 [= 4] for control) with occlusive neointimal lesions in small pulmonary arteries and arterioles (12, 13). In contrast to no contraction by l-NNA in normotensive pulmonary arterial rings, the NOS inhibitor caused marked contraction in hypertensive rings from SU5416/hypoxia/normoxia-exposed PH rats (Figure E1), which is similar to what is observed in pulmonary arterial rings isolated from chronically hypoxic rats (18). This phenomenon can be interpreted as evidence of high spontaneous tone that is opposed by endogenously produced nitric oxide in hypertensive pulmonary arterial rings under resting tensions in physiological salt solution. In other words, l-NNA unmasks the spontaneous contraction of hypertensive pulmonary arteries. All TKIs concentration-dependently and completely reversed the spontaneous contraction in pulmonary arterial rings isolated from SU5416/hypoxia/normoxia-exposed PH rats PROTAC ERRα ligand 2 (Figure 3B). Nilotinib and sorafenib were more potent than imatinib in reversing the U-46619Cinduced and the spontaneous contractions in normotensive and hypertensive pulmonary arteries, respectively. Open in a separate window Figure 3. Concentration-relaxation curves to tyrosine kinase inhibitors, imatinib (= 8), nilotinib (= 4), and sorafenib ( 0.001 versus sorafenib and nilotinib. Acute Hemodynamic Effects of Imatinib in Catheterized PH PROTAC ERRα ligand 2 Rats Compared with normotensive rats, SU5416/hypoxia/normoxia-exposed rats had very high RVSP (20 3 versus 100 5 mm Hg, respectively; = 4 and 11, respectively; 0.001) with markedly reduced cardiac index (CI) (119 12 versus 59 8 ml/min/kg, respectively; = 4 each; 0.001), normal LVSP (138 9 versus 140 6 mm Hg, respectively; = 4 and 11, respectively; not significant [n.s.]), and HR (372 23 versus 347 19 mm Hg, respectively; = 4 and 11; n.s.). All PH rats showed severe RV hypertrophy as reflected by high RV/LV+S ratio compared with normal rats (0.20 0.02 versus 0.55 0.02, respectively; = 4 and 11, respectively; 0.001). The acute effects of intravenous PROTAC ERRα ligand 2 imatinib (20 and 50 mg/kg, bolus) on RVSP, LVSP, and CI were tested in anesthetized SU5416/hypoxia/normoxia-exposed severe.