engleski

In vitro effect of zinc on SOD-like activity in different cell types

Activities of Cu,Zn superoxide dismutase (SOD) isolated from spermatozoa,polymorphonuclear leukocytes, erythrocytes and/or in intact cells exposed to different zinc (Zn) concentration were investigated. Cells were incubated (30 min,37C) in the presence of 20-1000umol/l Zn and subsequently washed, lysed by cold shoch procedure and analysed for SOD-like activity. In other set of experiments, the enzyme was first extracted from cells by cold shock and isolated SOD was then incubated in the presence of zinc under the same conditions. SOD-like activity was measured using xanthine/xanthine oxidase method. Cellular zinc content was measured using an atomic absorption spectrophotometer. Incubation with Zn resulted in a dose dependent decrease in spermatozoal SOD activity. The most pronounced decrease of SOD-like activity was obtained for enzyme permeabilized from spermatozoa and thenexposed to 1000 umol/l Zn. The remainining activity amounted 47% of the activity without zinc (100%)(1.42+0.2 vs 3.03+0.4 U/108 sperms; n=11;p<0.003) while the remaining SOD-like activity of intact spermatotoa exposed ti zinc was 63% (1.6+0.1 vs 2.6+0.3 U/108 spermatozoa; n=12; p<0.002). The SOD exstracted from polymorphonuclears was significantly decreased at 20umol/l Zn (0.94+0.2 vs 0.75+0.1 U/mg proteins; p<0.01, n=10), while therewas no change at 100 and 200 umol/l Zn (0.88+0.007 vs 0.87+0.008 and 0.77+0.03 vs 0.77+0.001 U/mg proteins,n=10). SOD of intact polymorphonuclears as well as SOD of intact and lysed human erythrocytes or commercial SOd from bovine erythrocytes (Sigma) remained unaffected by zinc. In conclusion, these results show that compared to other two cell types studied, spermatozoal SOD was the most sensitive to in vitro inhibitory effect of zinc.On the other hand, Sod from erythrocytes was resistant to such influence, while the SOD from leukocytes was affected by zinc, only when extracted from the cells.

zinc; SOD-like activity; cells

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