M7 PM Metals in the Environment: Aquatic Biological Perspectives
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 327-329

(GAL-1117-860194) The effects of natural organic matter on fish gill epithelia.

Galvez, F. ¹, Donini, A.¹, Diao, L. ¹, Playle, R.², Smith, S.³, Wood, C.¹, ¹ Department of Biology, McMaster University, Hamilton, Ontario, Canada² Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada³ Department of Chemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada

ABSTRACT- Natural organic matter (NOM) exhibits a high degree of chemical heterogeneity, conferring on it different abilities to complex metals. However, little is known of the direct effects of NOM alone on epithelial surfaces. We used in vitro and in vivo approaches to study the influence of different sources of NOM on the electrophysiological characteristics of the fish gill epithelium. NOM isolated from nine different sources in Ontario, as well as a commercially available humic acid (Aldrich), were tested for their effects on transepithelial potential (TEP) and resistance (TER) on a fish gill epithelium in primary culture on filter supports. Ion activities in the different waters were also measured using ion-selective electrodes to assess the relative chelating abilities of each source of NOM. NOM derived from allochthonous sources (Four Mile Creek, Talon Lake, Trout Lake, Luther Marsh and Sanctuary Pond) resulted in significant changes to the transepithelial potential (TEP) across a cultured surrogate model of the rainbow trout gill. In comparison, NOM derived from autochthonous sources (Dundas Sewage Treatment Plant, Grand River, Lake Erie and Lake Nippissing) elicited only marginal effects on TEP across the epithelium. NOM also influenced TEP in vivo in a similar fashion. The magnitude of these NOM-induced changes in TEP was related to the aromaticity of the NOM, although two of the NOM samples were particularly strong chelators of calcium, which in these cases could explain their abilities to hyperpolarize the gill epithelium. This talk will discuss the implications of these direct effects of NOM at the fish gill to the future development of environmental risk models for metals such as silver (Supported by Kodak Canada and NSERC).

Key words: natural organic matter, cultured gill epithelium, metal binding, transepithelial potential