Content of protein carbonyl groups in gerbil brain after reversible bilateral carotid occlusion: effect of 2,3-dihydromelatonin.

OBJECTIVES

To investigate whether a new derivative of melatonin, (2,3-dihydromelatonin (DHM), prevented the oxidative stress induced by ischemia /reperfusion (I/R) in the gerbil brain. To specify the effect on endogenous antioxidant activity and protein modification in the brain cortex, we evaluated the contents of glutathione (total GSx=GSH+GSSG) and protein carbonyl groups (PCG).

METHODS

Brain ischemia (I) was induced by (12 min) bilateral carotid occlusion (BCAO) in adult male gerbils (60-70 g b wt.) DHM (10 mg/kg) was administered i.p. 20 min before surgery, at the beginning of reperfusion (R), and then 2 and 6 hours later. Horizontal locomotor activity was recorded using the open-field test over the course of 24 hours. Contents of GSx and PCG were determined after 6h of reperfusion. Glutathione (GSx ) was determined spectrophotometrically using the microplate reader, lactate by the kit Randox, UK. The measurement of protein carbonyl (PCG) groups after their derivatization with 2,4-dinitrophenylhydrazine (DNPH) is the most widely used assessment of protein oxidation. The contents of PCG and malondialdehyde (MDA) were assayed spectrophotometrically.

RESULTS

Evaluation of the data obtained from horizontal locomotor activity recorded over the course of 24 hours using the open-field test showed that hyperactivity induced by I/R was returned by DHM almost to its control value during the interval of up to 6 hours (from 18,000 to 5,000 cm distance traveled, p<0.05). I/R decreased the content of GSx by 27.2% (p<0.001). Administration of DHM resulted in maintaining the content of GSx at control values (p<0.05). DHM diminished the I/R-induced increase in PCG in the cortex by 34.2% (p<0.01).

CONCLUSIONS

Our data indicate that the effect of DHM on the content of glutathione and protein carbonyl groups occurred during the first 6 hours of reperfusion. In this time interval both the content of GSx and protein carbonyl groups seem to be sensitive indicators of I/R-induced oxidative stress in the gerbil brain.