Effects of copper toxicity at different pH and temperatures on the in vitro enzyme activity in blood and liver of fish, Prochilodus lineatus

Blood and liver from curimbata (Prochilodus lineatus) acclimated at pH 4.5, 7.0 and 8.0 and at 20 and 30 degrees C were exposed in vitro to different concentrations of copper (Cu): 98 +/- 0.8 mu g Cu L-1 at pH 4.5 and 16 +/- 0.2 mu g Cu L-1 at pH 8.0 at 20 degrees C; 88 +/- 0.8 mu g Cu L-1 at pH 4.5 and 14 +/- 0.5 mu g Cu L-1 at pH 8.0 at 30 degrees C and in 29 mu g Cu L-1 at pH 7.0 at 20 and 30 degrees C for 2 h. The pH affected the levels of glucose and glycogen and in vitro exposure to Cu increased glucose levels and decreased glycogen at 20 and 30 degrees C. Exposures to acid water and Cu in vitro also resulted in an increase in enzyme activity in the blood, hexokinase (HK), pyruvate kinase (PK) and at pH 8.0 decreased the HK activity and increased PK and lactate dehydrogenase (LDH) activities at 20 degrees C. Cu caused an increase in the activities of HK (at pH 4.5) and PK in both pH, 4.5 and 8.0 at 30 degrees C. At 20 degrees C, HK (pH 8.0) and glycose-6-phosphate dehydrogenase (G6PDH) (pH 4.5) activities increased and PK (pHs 4.5 and 8.0) and LDH decreased (pH 4.5) in the liver. In vitro, exposure to Cu increased HK and G6PDH at pH 8.0 and PK activity increased in both pH values and LDH increased in pH 7.0. Cu exposure in vitro at 30 degrees C, phosphofructokinase (PFK) and PK activities decreased and LDH activity increased in all pH values when compared to fish from the water from its respective pH values. Interactions occurred in blood and liver between the temperature, pH and exposure to copper in vitro. The in vitro tests may constitute an interesting biological model for experimental and applied toxicology, especially in the case of environmental pollution. (AU)