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The relationship between oxygen and 1,2,4,5-tetrachlorobenzene uptake in five species of fishes

University of British Columbia

The studies presented in this thesis were designed to establish whether a relationship exists between the uptake of a model toxicant, 1,2,4,5-tetrachlorobenzene (TCB) and the rate of oxygen consumption (MO₂) in several species of fishes. If so, it is possible that toxicant uptake may be predicted from MO₂'s measured in the absence of the toxicant. There is no effect of environmental TCB concentrations on the oxygen consumption rate of resting or exercising adult rainbow trout, and body accumulations of the toxicant did not affect the maximal aerobic swimming velocity attained by juvenile rainbow trout. Thus, there is no direct effect of TCB exposure to complicate the relationship between oxygen and toxicant uptake at a variety of swimming velocities. The potential of estimating whole body accumulations of TCB from the toxicant concentration in plasma and 11 tissues was investigated in the anticipation of reducing the work otherwise required to measure whole body concentrations. The variability in TCB concentration of a given tissue, however, is sufficiently great to preclude the use of this method to estimate body burden. Plasma concentrations appear to be indicative of body concentrations following 2 hrs of TCB exposure, however, over longer exposure durations, this is not the case. Thus whole body concentrations can only be obtained through direct measurements. There is a relationship between the rate of oxygen consumption and the uptake rate of 1,2,4,5-tetrachlorobenzene (TCB) during initial toxicant exposure, in five species of fishes forced to swim at different velocities. The animals were exposed to two external TCB concentrations; however, standardizing for the external concentration was not sufficient to permit grouping of the data, likely as a result of an overestimation of the aqueous environmental TCB concentration. Because the data could not be grouped, a single coefficient to predict TCB uptake from MO₂ could not be calculated. The inclusion of the proportion of body lipid in the relationship describing toxicant uptake markedly improved the coefficient of determination, suggesting that either an elevated body lipid content increases TCB diffusivity at the gill, or that a limitation to the uptake of TCB in addition to that at the gills, may also exist at the level of the tissues. The establishment of the relationship between oxygen and TCB uptake implies a potentiality for the prediction of toxicant uptake in fish, as a function of the animals MO₂ which can be obtained from the literature. MO₂ for a variety of fish species, sizes and activity levels, in an assortment of environments have been compiled into a database, called OXYREF (Thurston and Gehrke, 1991). This could be a valuable tool for the prediction of toxicant uptake provided the relationship between toxicant and oxygen uptake is independent of fish size. Physico-chemical characteristics of xenobiotics are well documented and it is conceivable to incorporate a toxicant specific correction factor to predict the uptake of a range of xenobiotics in fish.

Text

2010-11-03

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http://hdl.handle.net/2429/29777

Zoology

University of British Columbia

Graduate