The purpose of the present study was to evaluate the hydrogen peroxide (H2O2) release by phagocytes from infected and uninfected mammary glands in dairy cows. Thus, milk samples from 73 quarters were divided in healthy and infected samples according to bacteriological culture and somatic cell count (SCC). After separation of milk cells, the samples were submitted to differential SCC and hydrogen peroxide release by oxidation of phenol red. There was a lower H2O2 release by phagocytes from infected quarters, as well as, a negative correlation between the H2O2 release by phagocytes and SCC (r=-0.34; P=0.0025) and percentage of neutrophils (r=-0.24; P=0.04). Furthermore, it was observed a tendency toward a lower H2O2 release by phagocytes stimulated by phorbol 12-myristate 13-acetate in the infected quarters. However, a higher H2O2 release by phagocytes was observed in milk samples from infected quarters by the estimation of the H2O2 release by phagocytes in 1mL of milk according to SCC mL-1 of each sample. The present study showed a decrease in H2O2 release by the infected quarters which indicate lower microbicidal activity. However, the higher H2O2 release by phagocytes in 1mL of milk in the infected quarters may contribute to recruitment of leukocytes to the site of infection and the persistence of infection.
bovine; mammary gland; mastitis; oxidative metabolism; phagocytes
