Tissue-specific changes in Ca2+-ATPase and Na+/K+-ATPase activities in freshwater African catfish Clarias gariepinus juvenile exposed to oxadiazon

Background: This study investigated the effect of sublethal concentrations (0.0, 0.3, 0.6, and 1.2 mg center dot L-1) of herbicide oxadiazon (ODZ) on the activities of Ca2+-ATPase and Na+/K+-ATPase in juvenile Clarias gariepinus. Methods: One hundred eighty juveniles of Clarias gariepinus (mean weight 58.88 +/- 1.24 g and mean length 22.34 +/- 1.52 cm) were randomly divided into four groups and exposed to sublethal concentrations (0.00, 0.3, 0.6, and 1.2 mg center dot L-1 ODZ) for 21 days in a static renewal bioassay system in which the herbicide and water were replaced completely every day. The changes in Ca2+- and Na+/K+-ATPase activities in the gill, kidney, liver, and heart of the fish were assayed on days 1, 7, 14, and 21. Result: The result showed significant alteration in the activity of these membrane-bound enzymes. There was duration and concentration-dependent significant (p < 0.05) increase in Ca2+-ATPase activity in the treatment groups when compared with the control. The Na+/K+-ATPase activity was significantly (p < 0.05) inhibited in all the tissues when compared with control. The observed alterations in the activities of both Ca2+-ATPase and Na+/K(+)ATPase in this study may be indication of impaired ionic transport and imbalance in the fish which may trigger other biochemical, physiological, and even neurological consequences that may compromise several body functions. Conclusion: The alteration of the ATPase activities in C. gariepinus by ODZ is likely to affect the ATP usage and energy metabolism in the fish serious repercussions on Ca2+ homeostasis, Na+/K+ sodium pump, and Ca2+/Na+ exchanger The results suggested that assay of the enzymes could be used as a biomarker of water pollution.