Osmotic Response of Cortisol Treated Fresh Water Fish ? Oreochromis mossambicus Exposed to Pesticides

The activity of osmotic organs is affected by the changes in the physico-chemical nature of the medium, which is altered by the extensive use of pesticides that affect osmotic balance. The present study is focused on the osmotic response of cortisol treated fresh water fish Oreochromis mossambicus, exposed to pesticides like lindane, nuvacrom and sevin. Membrane protein concentration of gill filaments shows mark increase when exposed to sub lethal concentration of pesticides due to histopathological alteration induced by pesticides. The Na+K+ATPase activity in gill filaments is enhanced by pesticide exposure. Pesticides induce stress which alters the ionic composition of external and internal milieu of fish. To recompense the change the fish responds by stimulating the osmotic organs like gills. It is reflected in the elevated rate of activity of branchial Na+K+ATPase. Cortisol treatment increases the membrane protein concentration and Na+K+ATPase activity, but the hike is not as great as that caused by pesticides. In vivo administration of cortisol to fishes, exposed to sub lethal concetration of pesticides, also stimulates the Na+K+ATPase activity. In this case it is very noteworthy that the Na+K+ATPase activity is brought to the normal level. The stress induced by pesticides is compensated by the hormone cortisol as evidenced in the attainment of normal activity of branchial Na+K+ATPase in hormone treated fishes exposed to pesticides. Pesticides polluting our water resources endanger the wonder-provoking biodiversity. This paper invites the attention of the public and the authorities concerned to expedite immediately legislative measures and effect public conscientisation against the indiscriminate use of pesticides.