Sublethal Effects of Organophosphate Diazinon on the Brain ofCyprinus Carpio

Abstract

Effects of diazinon, at different concentrations and exposure times, were investigated in freshwater fish, Cyprinus carpio, to elucidate the possible mode of action on lipid peroxidation together with the inhibitory effect of diazinon on acetylcholinesterase activity and changes in tissue protein levels. Cholinesterase inhibition is considered to be a specific biomarker of exposure to organophosphorus pesticides. Fish were exposed to 0.0036 microg/L, 0.018 microg/L, and 0.036 microg/L (sublethal) concentrations of diazinon for 5, 15, and 30 days, and biochemical measurements were carried out spectrophotometrically. Brain was chosen as an indicator tissue because it is a target system for the organophosphorus action. More than 20% decline in acetylcholinesterase activity relative to mean activity of the controls was observed in the diazinon-exposed groups. Protein content decreased significantly after 15 days of exposure to 0.018 microg/L and 0.036 microg/L diazinon and after 30 days of exposure to 0.036 microg/L. Malondialdehyde level declined markedly compared with the control levels. This study showed that prolonged exposures of C. carpio to diazinon had significant effects on brain acetylcholinesterase activity and that environmentally relevant concentrations of diazinon can significantly inhibit brain acetylcholinesterase activity. Altered protein content was probably due to the high energy demand under pesticide stress or inhibition of de novo enzyme synthesis. The decreased malondialdehyde content may reflect the possibility of better protection against oxidative stress.

Effects of diazinon on antioxidant defense system and lipid peroxidation in the liver of Cyprinus carpio (L.)

“…Fish were divided into four groups one of which, (control group) was held in tap water, and the others (treatment groups) were exposed to 0.0036, 0.018, and 0.036 ppb for 5, 15, and 30 days. The doses chosen were primarily used as a starting point because they not only cause substantial elevation of lipid peroxidation in the brain of C. carpio (Ozcan Oruc et al, 2006), but they are also believed to lead to low‐level toxicity for a long duration time in liver tissues.…”