[Vasodilating effects of NY-008 in ring preparation of rat aorta]

Vasodilating effects of NY-008 were compared to those of verapamil in isolated rat aorta. NY-008 at the dose of 3 x 10(-5) M relaxed 10-70 mM potassium chloride (KCl)-induced contraction. NY-008 relaxed preparations precontracted with 60 mM KCl concentration-dependently with an IC50 of (6.17 +/- 1.75) x 10(-6) M, and those precontracted with norepinephrine (NE) (10(-6) M) concentration-dependently, maximally by 90.0 +/- 2.86%, with an IC50 of (2.06 +/- 0.38) x 10(-5) M. At 10(-8)-3 x 10(-6) M, verapamil relaxed preparations precontracted with NE (10(-6) M) concentration-dependently, maximally by 55.9 +/- 5.56%. At 3 x 10(-5) M and 10(-4) M, NY-008 relaxed (10(-6) M)-induced phasic contractions in a Ca(2+)-free 1 mM EGTA-containing buffer, by 22.4 +/- 3.69% and 35.4 +/- 5.74%, respectively. In contrast, 3 x 10(-7) M verapamil did not. NY-008 concentration-dependently decreased the maximal responses to calcium chloride (CaCl2) in 60 mM KCl-depolarized preparations, and it shifted the ED50 values of CaCl2 to the right, whereas verapamil shifted the ED50 values of CaCl2 to the right without decreasing the maximal responses to CaCl2. At 10(-5)-3 x 10(-4) M, NY-008 concentration-dependently relaxed preparations precontracted with prostaglandin F2 alpha (10(-5) M) in a Ca(2+)-free, 0.5 mM EGTA-containing buffer, whereas 10(-7)-10(-5) M verapamil did not. These results suggest that NY-008 antagonized Ca2+ and decreased the Ca(2+)-sensitivity of contractile elements or inhibited contractile proteins in rat aorta.