Evaluation of the free ion activity model of metal-organism interaction: extension of the conceptual model

被引:120
作者
Brown, PL
Markich, SJ
机构
[1] Australian Nucl Sci & Technol Org, Environm Div, Menai, NSW 2234, Australia
[2] Univ Technol Sydney, Dept Environm Sci, Broadway, NSW 2007, Australia
关键词
free ion activity model; biological receptor theory; metal speciation; bioavailability; concentration-response;
D O I
10.1016/S0166-445X(00)00115-6
中图分类号
Q17 [水生生物学];
学科分类号
071004 ;
摘要
The present study integrates the concepts of the free ion activity model (FIAM) into biological receptor theory (BRT; i.e. pharmacodynamic principles) to obtain a more rigorous conceptual model; one that more precisely quantifies the interaction of chemical species at biological receptor sites. The developed model, which is viewed as an extended FIAM, explains the conditions under which the FIAM will be effective in explaining biological response (BR). It establishes that BR is directly proportional to the activity of the free metal ion in the linear regions of concentration-response curves only. Additionally, it indicates that {X-cell}, the activity of free surface sites on the cell membrane, does not need to be constant in the region of BR, as assumed by the original FIAM. The extended FIAM was tested by re-examining concentration-response data from the literature on aquatic organisms exposed to several ecotoxicologically-relevant trace metals. These data, which would be considered exceptions to the original FIAM, were found to be consistent with the extended FIAM. Due to its more rigorous conceptual basis, the extended FIAM is capable of modelling concentration-response experiments from a wider range of water chemistry conditions (i.e. varying pH, hardness and dissolved organic matter) than the original model and, as such, potentially provides a more useful tool for evaluating metal-organism interactions. This study proposes, for the first time, a quantitative method of uncoupling the biological effects of a metal hydroxide (1:1) complex from that of amelioration of the free metal ion (Mz+) by H+. Since the activities of H+ and metal-hydroxide cannot be independently varied, it has been previously very difficult to evaluate whether metal-hydroxide species contribute to eliciting a BR. Furthermore, the extended FIAM can directly derive fundamental information from concentration-response curves, such as the binding constants of H+ or the hardness cations (Ca2+ and/or Mg2+) to the cell membrane surface of aquatic organisms. (C) 2000 Elsevier Science B.V. All rights reserved.
引用
收藏
页码:177 / 194
页数:18
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