Effects of Cirsiliol, a Flavone Isolated from Achillea fragrantissima, on rat isolated smooth muscle

Abstract

The effects of the flavone cirsiliol on rat isolated phenylephrine-precontracted proximal aorta, acetylcholine-pre-contracted trachea, urinary bladder, and uterus were studied. Cirsiliol (10−8-3×10−4M) caused concentration-dependent relaxation of the rat isolated phenylephrine-precontracted proximal aorta, acetylcholine-precontracted trachea, urinary bladder and inhibited the phasic contractions and the tone of the uterus. Cirsiliol (3×10−5, 1×10−4 and 3×10−4M) shifted to the right epinephrine concentration-effect curves on the proximal aorta and significantly inhibited the maximum contractions induced by epinephrine in this preparation. In Ca2+-free, depolarizing salt solution, cirsiliol (3×10−5, 1×10−4 and 3×10−4M) also shifted to the right CaCl2 concentration-effect curves on the proximal aorta and inhibited the maximum contractions induced by 3×10−2M CaCl2 whereas it had no effect on epinephrine-induced contractions in Ca2+-free salt solution on the same preparation. These observations suggest that the inhibitory effects of cirsiliol on smooth muscle are attributed to inhibition of transmembrane Ca2+ influx and not due to inhibition by cirsiliol of Ca2+ release from intracellular stores or of Ca2+-binding to Ca2+-binding proteins of the contractile system.