THE EFFECT OF EXPOSURE TO 1,2,4,5-TETRACHLOROBENZENE AND THE RELATIONSHIP BETWEEN TOXICANT AND OXYGEN-UPTAKE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) DURING EXERCISE

These studies were designed to investigate the relationship between the initial uptake of a model toxicant, 1,2,4,5-tetrachlorobenzene (TCB), and the rate of oxygen consumption (MO(2)) in trout during exercise. There was no effect of environmental TCB concentrations ([TCB]) on the MO(2) 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. Rainbow trout were exposed to TCB for 1 h while swimming at different velocities and the [TCB] was measured in plasma and 11 other tissues. Tissue TCB concentrations were found to be extremely variable despite similar exposure conditions, likely due to differences in tissue lipid content. No one tissue was representative of body burden, but tissue TCB delivery appears to be directly related to the [TCB] in the plasma because at different swimming velocities the plasma:tissue TCB ratios remained constant despite regional changes in blood flow. After 2 h of TCB exposure, [TCB] in the plasma was equal to whole-body [TCB]; however, this relationship broke down after 6 h. Thus, whole-body TCB concentrations can only be obtained through direct measurement. There was a highly significant relationship (r(2) = 0.79) between MO(2) and TCB uptake rate during initial toxicant exposure in adult rainbow trout forced to swim over a large proportion of its aerobic potential. Thus, toxicant uptake in fish may be estimated based upon MO(2), which can be measured or can be obtained from the literature.