PARENT SESSION
TP8 - Fate & Effects of Metals: Aquatic Biology
Chair: Playle, Rick¹, ¹ Wilfrid Laurier University, Waterloo, ON
Co-chair: Green, Andrew², Lee, Chris³, ² International Lead Zinc Research Organization, Inc, Research Triangle Park, NC³ International Copper Association, Ltd., New York, NY
2:10 PM to 5:30 PM - Tuesday, 19 November 2002
Room Ballroom C

(468) Iono-regulatory distruption as the acute toxic mechanism for lead in rainbow trout (O. mykiss).

Rogers, J^*,1, Richards, J¹, Wood, C¹, ¹ McMaster University, Hamilton, ON, Canada

ABSTRACT- Relative to other metals, little is known regarding the acute toxic mechanism by which lead acts on fish. Circumstantial evidence suggests that a lead/calcium antagonism may exist. Therefore, to determine the mechanism of lead toxicity, iono-regulatory impacts were first assessed through unidirectional Na⁺, Cl^-, and Ca²⁺ flux measurements with radiotracers. Ca²⁺ flux measurements showed that lead exposure does reduce calcium uptake in fish exposed to the 96h LC₅₀ of 1 mgPb/l and to lower concentrations of 0.5 and 0.25 mgPb/l. Lead also impacted sodium and chloride uptake, although the mechanism is yet unclear. Studies using cannulated adult rainbow trout examined effects of 1 mgPb/l on blood gases, acid/base status, electrolyte balance, and hematology. While no disturbances in respiration, acid/base balance, hematocrit, or hemoglobin were observed, significant iono-regulatory disturbance occurred. Hypocalcemia was observed in lead-exposed fish in addition to reductions in plasma sodium and chloride levels. These findings are consistent with the disruption of ion uptake observed in flux experiments and support an iono-regulatory rather than respiratory mechanism of acute lead toxicity in rainbow trout. (Supported by NSERC Strategic, ILZRO, NiPERA, ICA, Falconbridge, Cominco, and Noranda)

Key words: rainbow trout, lead, acute toxicity, iono-regulation