Acyloxyacyl hydrolase activity of neutrophil leukocytes in normal early postpartum dairy cows and in cows with retained placenta

Acyloxyacyl hydrolase (AOAH) is an enzyme of bovine polymorphonuclear neutr ophil leukocytes (PMN) that is capable of detoxifying endotoxin (25). The a ctivity of AOAH in PMN isolated from the blood was investigated in dairy co ws that expelled the fetal membranes normally (Group NFM) and in cows with retained fetal membranes (Group RFM) to obtain better insight into the role of the AOAH enzyme of neutrophils in endotoxin-related diseases, which occ ur frequently in dairy cows during the early postpartum period, especially in RFM cows. Twenty early postpartum dairy cows were used in the study: 13 NFM cows and 7 RFM cows. In the RFM cows, the percentage of PMN in blood (2 9 +/- 4%) was significantly (P < 0.05) lower than in NFM cows (43 +/- 4%) T he average AOAH activity in RFM cows (mean +/- SEM = 89 +/- 13 pmol fatty a cid / 10(7) PMN / h) was lower than in NFM cows (107 +/- 6 pmol fatty acid / 107 PMN / h), but the difference in neutrophil AOAH activity between the 2 groups was not significant. There was also a higher percentage of immatur e neutrophils in isolated leukocyte suspensions from RFM cows (22 +/- 8%) t han from NFM cows (15 +/- 4%), so that impairment of AOAH activity in early postpartum cows could be explained, in part, by immaturity of the neutroph ils. These results suggest that the decreased AOAH activity of PMN could pl ay a role in the pathogenesis of endotoxin-related diseases in dairy cows d uring the early postpartum period. (C) 1999 by Elsevier Science Inc.