RAT اثرات مسموميت كوتاه مدت و تحت مزمن با سرب برمتابوليت هاي نيتريك اكسايد و پاسخ دهي عروقي در

Effects of Short-Term and Subchronic Lead Poisoning on Nitric Oxide Metabolites and Vascular Responsiveness in Rat

Objective: The aim of this study was to examine the short-term (4-8 weeks) and subchronic (12 weeks) lead poisoning on the levels of nitrite and nitrate (NOx) and vascular reactivity Material and Methods: Male Sprague-Dawley rats were divided to lead-treated and control groups. The lead-treated group was subdivided to 3 groups, in witch their drinking water contained lead acetate (IN ppm) for 4, 8, and 12 weeks. Blood pressure was monitored using rat tail electro sphygmomanometer in each group. Vanadium chloride (VC13) was used to reduce nitrate to nitrite, followed by spectrophotometer analysis of total nitrite using Greiss reagent. In vascular reactivity experiments thoracic aorta was removed and after stabilization in organ bath, effects of contractile (phenylephrine, clonidine) and relaxant (isoproterenol) agents in the absence and presence of relative antagonists was evaluated. Results: Short-term lead administration was accompanied by significant elevation of blood pressure and reduction in level of serum NOx. At the end of subchronic lead poisoning the trend of decrease in NOx was reversed despite further increase in blood pressure. Both short-term and subchronic lead administration resulted in significant changes in vascular reactivity with respect to either vasoconstrictor (phenylephrine) or vasodilator (isoproterenol) agents. Conclusion: Altogether, it can be concluded that blood pressure increases even in the earliest phases of lead poisoning. Probably, the same mechanisms involved in chronic phases of lead poisoning such as nitric oxide pathway and vascular adrenergic system are also operative in short-term and subchronic phases of lead poisoning.