Protective effect of endogenous melatonin and exogenous melatonin in pinealectomized rats on toxicity induced with organophosphate insecticide

Fenthion is an organophosphate insecticide which has been used for many years. Yet studies on the harmful effects of fenthion and their prevention are still being conducted. The aim of this study is to evaluate toxicity induced through acute fenthion exposure and the protective quality of exogenous and endogenous melatonin. This will be tested using following parameters; superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA). 63 male rats from genus of wistar-albino were separated into 6 groups where control group had 8 rats while other groups were given 11 rats each: control (G1), fenthion (G2), fenthion + melatonin (G3), pinealectomy (G4), pinealectomy+fenthion (G5), pinealectomy+fenthion+melatonin (G6). In order to observe the effects of endogenous melatonin, fenthion was administered orally one day before with a dosage of 54mg/kg. Melaronin was administered for two days intraperitoneally during daytime in a single dose of 10 mg/kg. 24 hours following the application of fenthion, rats were sacrificied. Liver, kidney and brain tissue samples' SOD, CAT and enzyme activities and MDA levels were determined with spectrophotometric method. Statistical comparison of two independent groups were done with Mann-Whitney U test and whenever more than two independent groups were compared, Kruskal- Wallis H test was used. Meaningfulness level was determined to be p<0.05. Upon administariton of fenthion on liver tissue, a significant increase in G2 CAT and MDA values was detected while no significant difference was observed in SOD enzyme values. (CAT; PG1-G2=0,002; PG2-G3=0,006) (MDA; PG1-G2=0,032; PG2-G3=0,003). G6 Liver SOD enzyme activity recorded a significant decrease compared to G4 and G5. (PG4-G6=0,008; PG5-G6=0,011). G1-G2-G3 kidney groups showed no significant difference in their CAT and SOD activities. Pinealectomized groups' CAT and SOD values had a significant increase compared to other groups. (CAT; PG1-G4=0,032, PG1-G6=0,039) (SOD; PG2-G5=0,041, PG3-G5=0,045). Fenthion application on brain tissue resulted in a significant increase in (G2)'s SOD activitiy while application of melatonin in (G3) caused it to move to normal levels. (CAT; PG2-G3=0,026, SOD; PG1-G2=0,048, PG2-G3= 0,030, MDA; PG2-G3=0,009). Administration of fenthion to rats caused an apparent oxidative damage in liver and brain tissues while the oxidative damage was mild in the kidney and therefore we have observed changes in SOD and CAT enzyme activities and an increase in the MDA levels. Exogenous melatonin which was given at midnight when the endogenous melatonin secretion was high, greatly prevented oxidative damage in tissues however it was observed that pinoalectomized rats did not see enough anti oxidative effect of exogenous melatonin.