Effect of conservation time on bovine polymorphonuclear leukocytes in calves blood on oxidative burst and Escherichia coli phagocytosis activity

Abstract

The time effect on oxidative burst and phagocytosis of Escherichia coli by polymorphonuclear leukocytes of 5 healthy calve blood samples were evaluated. Samples were kept on ice bath for two (t2), four (t4), six (t6), twelve (t12) and 24 hours (t24) before the tests. The oxidative burst was measured using the 2',7'-dichlorfluorescein-diacetate (DCFH-DA) and E.coli as stimulus, also the same bacteria was used to phagocytosis process. The PMN basal oxidative burst of calves blood samples were analyzed by flow cytometry and were higher at times t4, t6 and t12 (p<0,05) than at t2. The oxidative burst fluorescence intensity induced by bacteria was higher at the times t4 and t6 than at t2 (p<0,05). The comparison between the basal oxidative burst and the one induced by bacteria on each time, showed t2 time as the one with the highest difference, with geometric media and standard deviation of 18,3 ± 4,4 and 26,7 ± 1,8 (p< 0,05), respectively. Phagocytosis activity was measured by fluorescence intensity and was higher on samples kept on ice bath for 6 hours than those at t2, t4 and t12 (p<0,05). The phagocytosis percentage did not differ between the different times. The ideal time to test the oxidative burst was 2 hours (t2). Further researches are necessary to verify the conservation time influence on E.coli phagocytosis by PMN of bovine blood.