The aim of the present study was to investigate the vascular effects of the
E‐isomer of methyl cinnamate (E‐MC) in rat isolated aortic rings and the putative mechanisms underlying these effects. At 1–3000
μmol/L, E‐MC concentration‐dependently relaxed endothelium‐intact aortic preparations that had been precontracted with phenylephrine (PHE; 1
μmol/L), with an IC
50 value (geometric mean) of 877.6
μmol/L (95% confidence interval (CI) 784.1–982.2
μmol/L). These vasorelaxant effects of E‐MC remained unchanged after removal of the vascular endothelium (IC
50 725.5
μmol/L; 95% CI 546.4–963.6
μmol/L) and pretreatment with 100
μmol/L
NG‐nitro‐l ‐arginine methyl ester (IC
50 749.0
μmol/L; 95% CI 557.8–1005.7
μmol/L) or 10
μmol/L 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (IC
50 837.2
μmol/L; 95% CI 511.4–1370.5
μmol/L). Over the concentration range 1–3000
μmol/L, E‐MC relaxed K
+‐induced contractions in mesenteric artery preparations (IC
50 314.5
μmol/L; 95% CI 141.9–697.0
μmol/L) with greater potency than in aortic preparations (IC
50 1144.7
μmol/L; 95% CI 823.2–1591.9
μmol/L). In the presence of a saturating contractile concentration of K
+ (150 mmol/L) in Ca
2+‐containing medium combined with 3
μmol/L PHE, 1000
μmol/L E‐MC only partially reversed the contractile response. In contrast, under similar conditions, E‐MC nearly fully relaxed PHE‐induced contractions in aortic rings in a Ba
2+‐containing medium. In preparations that were maintained under Ca
2+‐free conditions, 600 and 1000
μmol/L E‐MC significantly reduced the contractions induced by exogenous Ca
2+ or Ba
2+ in KCl‐precontracted preparations, but not in PHE‐precontracted preparations (in the presence of 1
μmol/L verapamil). In addition, E‐MC (1–3000
μmol/L) concentration‐dependently relaxed the contractions induced by 2 mmol/L sodium orthovanadate. Based on these observations, E‐MC‐induced endothelium‐independent vasorelaxant effects appear to be preferentially mediated by inhibition of plasmalemmal Ca
2+ influx through voltage‐dependent Ca
2+ channels. However, the involvement of a myogenic mechanism in the effects of E‐MC is also possible.
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