Ameliorative effect of quercetin in lead-induced toxicity on pulmonary artery of goat ( Capra hircus )

There is no level of blood lead (Pb) which can be regarded as safe for animals or humans; deleterious effects of Pb in the form of endothelial dysfunction, hypertension, cardiovascular dysregulation, and autonomic dysfunction have largely been documented. Lead, being a highly toxic heavy metal, affects nearly most of the organs and systems within an organism's body. Previous studies suggested quercetin, a normal dietary flavonoid, has a remarkable relaxing effect on smooth muscles of lung tissue. The smooth muscle rings, both untreated (control) and treated with Pb acetate were subjected to 5-HT and PE (contractile agents) and ACh and SNP (relaxing agents) both with or without the presence of quercetin in increasing doses. If, the Pb acetate is not present, the mean EC 50 values related to 5-HT and PE were 7.359 x 10-6 M and 5.953 x 10-6 M, respectively. In the presence of Pb acetate in solution, these values decreased to 9.140 x 10-7 M and 3.164 x 10-6 M, respectively, indicating a shift towards the left in the curve. The mean values of IC 50 for ACh and SNP were 2.445 x 10-8 M and 2.764 x 10-6 M, respectively, in the absence of Pb acetate. In the presence of Pb acetate in solution, these values increased to 5.258 x 10-7 M and 2.800 x 10-6 M, respectively, indicating a right shift in the curves. This shows the increase in the contractile nature of tissue due to Pb. In quercetincontaining solution, the values of mean EC 50 for 5-HT and PE were increased to 1.631 x 10-6 M and 1.167 x 10-5 M, respectively indicating a right shift in the curve. Likewise, IC 50 values were decreased to 4.730 x 10-8 M and 9.993 x 10-7 M, respectively, for ACh and SNP indicating a shift in the curve towards the left. This suggests quercetin has an ameliorative effect against the toxic effect of Pb on the pulmonary artery of goats by vasorelaxation.