The effects of acid and acid/aluminum exposure on circulating plasma cortisol levels and other blood parameters in the rainbow trout, Salmo gairdneri |
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Authors: | G G Goss C M Wood |
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Institution: | Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, Canada L8S4K1 |
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Abstract: | Softwater (Ca2+=50, Na+= 50(μequiv. l?1) acclimated rainbow trout were fitted with chronic arterial catheters to allow for repetitive blood sampling. After 48 h recovery they were then exposed to either control (pH 6.5, Al = 0μg l?1), acid (pH 4.8, Al = 0μg l?1) or acid plus aluminum (pH 4.8, A1 = 112 μg l?1) conditions for 72 h. Parameters measured included blood glucose, lactate, haemoglobin, haematocrit and plasma Na+, Cl?, protein and cortisol. Exposure to pH 4'8 alone caused no mortality, a moderate ionoregulatory disturbance and a transient elevation in plasma cortisol. All other parameters were not significantly different from controls. Addition of aluminum to this exposure caused 100% mortality with a mean survival time of only 27.0 h. There was a marked decrease in plasma ions, hyperglycemia, lactate accumulation, haemoconcentration, red cell swelling, and a sharp rise in plasma cortisol becoming greatly increased as the fish neared death. The mechanism of toxicity of acute acid/aluminum exposure, the role for cortisol under such conditions, and the validity of cortisol and glucose as indicators of stress in fish are discussed. |
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