The novel phenylpropiophenone derivates induced relaxation of isolated rat aorta.

Our aim was to define how different chemical properties of newly developed phenylpropiophenone derivates (PhPds) influenced their potency and efficacy to relax rat aorta. A contribution of ion channels in the PhPds and propafenone mechanism of vasodilatation was tested. PhPds were syntethysed by substitution in the benzyl moiety with -F, -CH3 or -CF3 groups on the ortho or para position. The vasodilatation by PhPds was examined on the rings of rat aorta precontracted with phenylephrine. In order to test involvement of voltage-gated Na+ and K+ channels and L-type Ca2+ channels in a mechanism of action of PhPds, we used their blockers: lidocaine, nifedipine and 4-aminopiridine, respectively. Aorta was more sensitive to 5-ortho-trifluoromethyl derivate than to propafenone and other PhPds. The 5-para-methyl derivate had lower potency and efficacy than propafenone and other PhPds. Lidocaine did not influenced relaxation induced by PhPds, but slightly inhibited the effect of propafenone. The 4-aminopiridine only inhibited relaxation induced by 5-para-methyl derivate. Nifedipine inhibited relaxation of the rat aorta induced by 5-ortho-trifluoromethyl derivate and by propafenone. Introduction of 5-ortho-trifluoromethyl and 5-para-methyl group in the benzyl moiety of propafenone molecule changed its potency, efficacy and mechanism of action in the rat aorta. The 4-aminopiridine- and nifedipine sensitive ion channels are involved in mechanism of action of 5-para-methyl and 5-ortho-trifluoromethyl derivate. The introduction of other tested groups in the benzyl moiety does not affect pharmacological properties of the PhPds in relation to propafenone.