THE EFFECTS OF SUPERMETHRIN ON AMMONIA-UTILIZING ENZYMES OF RUMEN BACTERIA

Synthetic pyrethroids are neuroactive substances with high selectivity to insects. They are fast-degrading and show low toxicity to the othe r organisms. In spite Of all these characteristics there are certain r isks for ruminants in these chemicals because the ruminants as herbivo rous animals consume large amounts of plants treated with insecticides . As bacterial microflora plays an important role in ruminant physiolo gy, the effects of supermethrin were investigated in relation to the a ctivity of key enzymes of nitrogen metabolism of rumen bacteria, namel y of glutamate dehydrogenase (GDH-NADH E.C.1.4.1.2., GDH-NADPH E.C.1.4 .1.4.) and glutamine synthetase (GS E.C.6.3.1.2.). Supermethrin (Czech oslovak product) was administered to 15 sheep of the Slovak Merino bre ed at the age of eight months, at subchronical doses (50 - 300 mg/kg l ive weight) for six weeks. Two bacterial fractions were isolated from rumen after sheep slaughter: rumen fluid bacteria and rumen-wall adher ing bacteria, in which GDH and GS activities were determined. The acti vities of these enzymes in eight pure bacterial rumen cultures were in vestigated to determine the effects of supermethrin on the different b acterial strains: S. ruminantium A 17, F succinogenes 16 J, B. ruminic ola 3/3, M. elsdenii 4 MJ, L. plantarum MRS, S. bovis A 24, S. xylosus 3 1 0 and E. faecium 2. The bacteria were cultivated in media with su permethrin additions at concentrations of 0.66; 1.66 and 6.6 mg/ml of the nutrient medium. The results have demonstrated that the dietary su permethrin did not have any significant effects on the investigated en zymes in rumen fluid bacteria. The activities of specific GDH-NADH ran ged from 274 +/- 58 to 290 +/- 84 nkat/mg of protein, the activities o f specific GDH-NADPH ranged from 37 +/- 4 to 55 +/- 0.9 nkat/mg of pro tein. The activity of the enzymes of rumen-wall adhering bacteria decr eased significantly. An addition of 50 mg of dietary supermethrin decr eased the activity of GDH-NADH from 1171 +/- 161 to 302 +/- 118 nkat/m g of protein, the activity of GDH-NADPH from 200 +/- 120 to 39 +/- 10 nkat/mg protein. The GS activity was fully inhibited. Supermethrin exe rted different effects on pure strains of rumen bacteria. The activity of GDH-NADPH was significantly inhibited only in F succinogenes and t he GS activity only in S. xylosus.