Inhibition of Na+-K+-ATPase in different tissues of freshwater fish Channa punctatus (Bloch) exposed to monocrotophos

Freshwater fish, Channa punctatus, commonly known as the snakehead fish, was exposed to two sublethal concentrations (0.96 and 1.86 mg/L) (selected on the basis of 1/20 and 1/10 of 96 h LC50 value) of monocrotophos for two exposure periods (15 and 60 days). Effects of monocrotophos on Na+, K+-ATPase in liver, kidney, muscle, intestine, brain, heart and gills were determined. Results indicate that Na+, K+-ATPase activity in tissues decreased as concentration of monocrotophos and exposure period increased. Monocrotophos induced significant inhibitory effects on the Na+, K+-ATPase activity of C punctatus, ranging from gills (70%) > Kidney (63%) > brain (57%) > intestine (52%) > liver (50%) > muscle (47%) > heart (44%) inhibition at a sublethal concentration of 0.96 mg/L. Significant inhibition was detected in Na+, K+-ATPase activity, ranging from gills (90%) > heart (78%) > kidney (78%) > muscle (74%) > intestine (71%) > brain (67%) > liver (63%) at sublethal concentration of 1.86 mg/L. After subacute exposure (15 days) only gills and brain showed significant inhibition after higher concentration (1.86 mg/L. However, it is evident that exposure duration is more important than dose in the inhibition of the activity of enzyme. At lower concentration initial stimulation of the activity of Na+, K+-ATPase activity was also noticed. It is suggested that the inhibition of the ATPase by monocrotophos blocked the active transport system of the gill epithelial as well as chloride cells, glomerular and epithelial cells of the tubules and thus altered the osmoregulatory mechanism of the fish. In fact, the impairment of the activity of enzymes which carry out key physiological roles could cause alterations of the physiology of the whole organism. (C) 2008 Elsevier Inc. All rights reserved.