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  • Title: Dietary silica modifies the characteristics of endothelial dilation in rat aorta.
    Author: Oner G, Cirrik S, Bulbul M, Yuksel S.
    Journal: Endothelium; 2006; 13(1):17-23. PubMed ID: 16885063.
    Abstract:
    Considering the importance of nitric oxide generation in the regulation of vessel tone, reduced endothelial nitric oxide synthase (eNOS) expression in alveolar macrophages exposed to short-term silica (Si) suggests the possibility of Si-induced changes in endothelial functions. In this experimental study, the functional changes of the endothelial cells were investigated in the aortic rings of rats subjected to 50 mg Si/kg body weight in their drinking water for 8 days. Norepinephrine elicited contractility and dilation response to acetylcholine (ACh) was significantly high in the aortic rings of Si-treated group. Alteration in receptor-independent endothelial response to A23187 in the aortic rings of Si-exposed rats was less obvious, but sodium nitroprusside (SNP)-elicited dilation was reduced significantly. A23187-induced relaxation was fully eliminated with N-nitro-L-arginine methyl ester (L-NAME) pretreatment, whereas 19.24 +/- 4.36% of ACh response was L-NAME resistant and eliminated with 10-5 M tetraethylammonium (TEA). Despite a significant reduction in the share of NO, the contribution of indomethacine (IND)-sensitive relaxation to ACh response remained unchanged in Si group. As a result, our findings demonstrated that Si both modifies the characteristics of endothelial relaxants and attenuates smooth muscle cell responsiveness to NO. Si-induced reduced NO association with elevated endothelium-derived hyperpolarizing factor (EDHF) in response to ACh, together with reduced NO sensitization, might have clinical importance in cardiovascular pathology.
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