有機毒性物質之混合效應及基質濃度之影響

Abstract

大腸菌為細菌性生物中極為普遍且具代表性之菌種,以大腸菌進行混合毒 性之研究,可了解物質之混合毒性對食物鏈中相關生物之影響.而若此類生 物遭受毒害,勢必牽動食物鏈而影響到其他位於高階之生物,包括人類本 身.有機毒物依據log P-QSARs(Quantitative structure-activity relationships)模式可分為反應性有機物以及非反應性有機物.本研究採 用13種反應性有機物,以及4種非反應性有機物,以大腸菌為實驗物種,分別 進行混合毒性實驗.結果發現,以毒性物質之劑量-反應曲線斜率配合 QSARs,可以有效地預測混合毒性結果.不同機制之反應性有機物彼此間的 混合,若兩者之劑量-反應曲線斜率均小於2,則有發生毒性加強的危險.若 兩者中有一者斜率大於3,則較有可能發生毒性減弱的現象.而對於非反應 性有機物間的混合毒性研究發現,若兩者具有近似的斜率,混合結果多為毒 性相加;反之,則多為毒性減弱.此結果與利用Microtox為實驗物種時相同. 表示相同的預測方法可以同時應用於不同物種上.另一方面,以不同的基質 濃度(1500mg/l及180mg/l COD)加入大腸桿菌中進行混合毒性實驗.結果發 現,不同的基質濃度下會有不同的混合毒性結果.當基質濃度改變時,若劑 量-反應曲線斜率沒有改變,則混合毒性結果不會改變;反之,則有大約1/4 之混合毒性結果會隨劑量-反應曲線斜率之改變而改變.本研究建立一系列 大腸菌對有機毒物之單一 雂帣V合毒性的數據和資料,發展出推測混合毒 性效應之準則,並與過去以Microtox試驗為基礎之預測準則比較.此外,亦 證明混合毒性會因基質濃度而改變,其主要影響原因為基質濃度造成劑量- 反應曲線斜率改變所致. The combined effects of organic chemicals were evaluated using E.coli'sS.OUR ( specific oxygen uptake rate ) test. There are 13 reactive toxicantsand 5 non-reactive toxicants used in this study. A set of useful criteria for the prediction of the combined effects of organic chemicals has beenestablished. This criteria were derived based on the quantitative structure- activity relationships ( QSARs ) of chemicals,and the slopes of chemicals'dose-response curves. For two reactive chemicals having different toxicmechanisms, opportunities of synergism increase obviously as both of theslopes less than 2; as one of the slopes greater than 3, the main jointaction were antagonism. For two non-reactive chemicals, similar slopesusually resulted in simple addition; different slopes resulted in antagonism. The effects of the nutrient concentration on mixture toxicity had been explored, too.It is apparent that the combined effects of organic mixtures were different as the nutrient concentration ( 1500mg/l and 180mg/l COD ) changed. In addition, it was found that 1/4 joint actions changed as nutrient concentration altered the chemicals' slope; none wasdifferent as nutrient concentration didn't alter the chemicals' slope. Aset of criteria for the prediction of multiple toxicity has been derived,and it was consistent in E.coli and Microtox. We also proved that nutrientconcentration will affedt the combined effects of organic toxicants and themain factor was slopes of dose-reponse curve.