ABSTRACT
To investigate the relaxing effect of ethanolic and aqueous extracts of Achillea fragrantissima in rabbit aortic rings by investigation their effect on calcium movement through smooth muscle in which intracellular calcium concentrations increase during the phase of contraction. Firstly: to elucidate the role of alpha1 adrenoceptors, a phenylephrine [PE] concentrationresponse curve was constructed in isolated rabbit aortic rings. Afterwards, the curve was repeated in presence of gradual- increased concentration of plant extract. The study was performed after checking the validation of this protocol. Secondly, contraction of rabbit aortic rings were done by high K[+] Krebs solution [35 mM], then the extract was added cumulatively. There was a comparison with standard vasodilators: Prazocin, Nitroglycerine and Diltiazem as references. The data showed an inhibition of this curve by the extracts with maximum effect for ethanolic one and the inhibition was for the maximum effect [E[max]] to P.E. Indeed, the extracts have also shown a relaxing effect on aortic rings precontracted by high concentration of K[+] ions. These data imply that the relaxing effect of the extracts includes an inhibition for calcium - induced contraction. The study should further continued to examine a possible effect of extract on calcium storage inside the cell
ABSTRACT
The vasodilator effect of ethanolic extract of Achillea Fragrantissima [Asteraceae] was detected at several levels in isolated and phenylephrine- precontracted rabbit aortic rings. First, The role of potassium channels and beta[2] receptors was determined by using the selective blockers for each of them: Charybdotoxine and Propranolol, respectively. Secondly, there was a set of experiments in which a Ca[+2] free Krebs solution was used and pheylephrine contracted the rings following by re-injection of Ca[+2] ions to the medium, this step was repeated in the presence of the extract. The vasodilator drugs: Diltiazem and Prazocine were used as reference and for evaluation. This extract showed a profound relaxing effect on phenylephrine- precontracted aortic rings, which was partially related to potassium channels and beta[2] receptors. In experiments that used Ca[+2] free Krebs solution, the extract inhibited partially the first phase contraction [pheylephrine contraction] and the second phase contraction which is due for calcium entry via calcium channels, with more potent for the last one and this was similar to Diltiazem. The vasodilator effect of ethanolic extract of Achillea Fragrantissima is largely related to calcium channels and this emphasis the need for isolation of related compound[s].