长期染砷致家兔肝脏蛋白巯基水平及巯基代谢相关酶活力下降

目的 探讨长期砷暴露对家兔肝脏蛋白巯基水平及与巯基代谢相关酶活力的影响及机制。方法 家兔以自由饮水方式慢性暴露于无机3价砷（iAs^Ⅲ）及5价砷（iAs^Ⅴ），18周后，测定肝脏组织中蛋白巯基、非蛋白巯基、硫氧还蛋白（TRX）水平，以及硫氧还蛋白还原酶（TR）、谷胱甘肽还原酶（GR）活性，同时检测血、尿及毛发中无机砷及其代谢产物甲基砷（MMAs）和二甲基砷（DMAs）。结果 经过18周的砷暴露，两个染毒组血和尿中iAs、MMAs、DMAs以及毛发中iAs、DMAs均显著高于对照组；iAs^Ⅴ组血中iAs、MMAs及尿中MMAs水平显著低于iAs^Ⅲ组，而尿及毛发中iAs水平显著高于iAs^Ⅲ组。iAs^Ⅴ组总巯基及蛋白巯基水平显著低于对照组。iAs^Ⅵ组TRX水平、TR及GR活力以及iAs^Ⅲ组TR活力与对照组相比亦显著下降。结论 家兔长期砷暴露导致肝脏中蛋白巯基水平及与巯基代谢密切相关的TR、GR活力显著下降，提示慢性无机砷暴露会引起肝脏内氧化及抗氧化失衡从而引发组织氧化损伤。

Decreased enzyme activities of hepatic enzymes concerning sulfhydryl metabolism and level of sulfhydryl in proteins by prolonged exposure of rabbit to inorganic arsenate

Objective To discuss the impacts and mechanism of variation of enzyme activities of hepatic enzymes concerning sulfhydryl metabolism and level of sulfhydryl in proteins by prolonged exposure of rabbit to inorganic arsenate.Methods Male New Zealand white rabbits were exposed to pentavalent arsenate(iAs V )and trivalent arsenite(iAs III )5mg/L for18weeks,respectively.Levels of thioredoxin,protein and non-protein sulfhydryl and the activity of thioredoxin reductase(TR)and glutathione reductase(GR)in liver,and the levels of inorganic arsenic(iAs),monomethylarsonic acid(MMAs)and dimethylarsinic acid(DMAs)in blood,urine,and hair were measured after that.Results MMAs and DMAs in blood and urine as well as levels of iAs and DMAs in hair of the two exposure groups were significantly higher that those of control.Levels of iAs and MMAs in blood,and MMAs in urine of iAs V group were markedly lower than those of iAs III group,while level of iAs in urine and hair were significantly higher than those of iAs III group.Levels of total and protein sulfhldryl of iAs V group,level of TRX and activity of TR and GR of iAs V group and activity of TR of iAs III group were significantly lower than those of control.Conclusions Prolonged exposure of rabbit to inorganic arsenate could induce decrease of protein sulfhldryl in liver and the activity of hepatic enzymes concerning with the sulfhldryl metabolism,which indicates that the unbalance of anti-oxidation system might be induced by prolonged arsenic exposure leading to final oxidative damages to the liver.