ARI Volume 2 Number 1.pdf - Zoo-unn.org

Superoxide dismutase (sod) activity and serum calcium level in rats 263buffer (0.2 mol/l). The mixture was shaken on a“cyclomixer”, and the absorbance read at 530 nmagainst water as blank.Statistical Analysis: Mean values (± SD) ofduplicate experiment with duplicate sampling (N =4) were taken for each analysis. Significantlydifferent results were established by one – wayANOVA and differences between groups, age, andconcentrations were determined by DUNCANmultiple range test. The accepted value ofsignificance was p 0.05) within the groups(NWR, MAR and AR) of experimental rats and thecontrols.The specific activity of SOD did notsignificantly increased in the NWR groups fed with1 %, 5 % or 10 % (w/w) – contaminated dietrelative to control (P > 0.05). In the contrary, theMAR groups and AR groups fed with 1 %, 5 % or10 % - contaminated diet showed significantincrease in the specific activity of SOD (P < 0.05)relative to their controls. Pair wise comparisonbetween NWR/MAR, NWR/AR and MAR/AR groups,fed with 1 %, 5 % or 10 % (w/w) insecticide –contaminated diet between 7 – 21 days ofexposure showed significantly different results (P< 0.05) on SOD only at 10 % (w/w) insecticide –contaminated diet; but the 1 % and 5 % (w/w)insecticide – contaminated showed non significantdifference (P > 0.05) (Table 3).Serum Ca 2+ levels is shown in Figure 1.The results were not significantly different withinthe groups fed with 1 % and 5 % of theinsecticide – contaminated diet (P > 0.05). Theresults were however significantly different withinthe groups NWR, MAR and AR fed with 10 % ofthe insecticide – contaminated diet (P < 0.05).Comparison of the effect of the insecticide on Ca 2+levels between the pairs of NWR/MAR, NWR/ARand MAR/AR groups showed significantly differentresults (P < 0.05) at 10 % concentration ofinsecticide-contaminated diet (Table 3).DISCUSSIONThe effect of pesticides on non-target organisms iswell documented (Moreby and Southway, 1999).The present study reports the effect of permethrin(formulated as “Rambo” insect powder) on nontargetorganisms. Our results demonstrated thatSOD activity decreased in the middle-aged rats(MAR) and aged–rats (AR) groups. The newly –weaned rats (NWR) groups showed a markedincrease in the SOD activity when compared withthe control. These differences in plasma SODlevels may be due to several factors, such as age,concentration of toxicants, sex, diet etc. The lowlevels of SOD in the plasma of MAR and AR ratsfed with insecticide-contaminated diet may be dueto the overwhelming influence of superoxideradicals or activated metabolites generated by theinsecticide exposure on the cell membrane of theexposed rats. Determination of SOD in plasmaprotein samples is based on the ability of theenzyme to inhibit superoxide anion- dependentreactions (Marklund and Marklund, 1974).The increase in SOD activity in the NWRgroups may be due to an induction of the enzymeprotein in the presence of reactive metabolites ofpermethrin (Ledig and Doffoel, 1988). This isobvious from the results in Table 2 where theplasma protein level for NWR fed with varyingconcentration of the insecticide in the diet weresignificantly high than that of the control. Similarly,Deuterman (1980) showed that at birth and at theearlier stage of life, there was a marked increasein the activity of many enzymes in the bodysystem of rats. These enzymes are involved inmany reactions relating to xenobiotic metabolismand more so, a number of them are agedependent.The increase in enzyme activity at anearlier stage in life may suggest that NWR groupswith increase level of SOD activity couldmetabolize the permethrin such that its putativetoxic effect was not overwhelming to subjugatethe mechanism of action of SOD. SOD is anextremely potent antioxidative enzyme that fightscellular damage arising from free radical inductionof reactive metabolites from oxidation ofhydrocarbon compounds (Onwurah and Eze,2000). Hence, induction of SOD activity in rats’blood plasma when exposed to environmentaltoxicants such as “Rambo” insecticide may be anadaptive mechanism for its survival. The rate atwhich individual and/or groups of rats metabolizedthe toxicant is age-dependent. This is justified bythe mortality ratio (1:4) of rats in favour of newlyweaned rats when compared with aged rats. SODactivity is also induced by diverse stresses (Bowleret al., 1992) which may include exposure tohydrocarbon compound, copper, ultra-violetradiation, thermal pollution, disease etc.