Elevated levels of β-hydroxybutyric acid in periparturient cows and in vitro effect on respiratory burst activity of bovine neutrophils

Abstract

The in vitro effect of normal (0.01 to 1 mM) and subketotic (1 to 2.5 mM) doses of butyric acid on the respiratory burst activity of bovine polymorphonuclear leucocytes (PMNL) isolated from blood was studied by luminol-enhanced, PMA (phorbol-12-myristate-13-acetate)-induced chemiluminescence (CL). The subketotic concentrations of butyric acid induced a significant inhibitory effect on CL. In a cell free assay, consisting of sonicated cells and H 2O 2, no changes in activity could be observed. The activity of the myeloperoxidase was not significantly altered as shown by the ortho-dianisidine-oxidation assay. Also, the production of O 2 − measured by the cytochrome c reduction assay was not affected by different doses of butyric acid. Butyric acid had no scavenging effect on hypochlorite. The reason for the inhibitory effect on CL may be a decreased production of H 2O 2. Indeed, luminol-enhanced CL evaluates the production of H 2O 2. This could not be confirmed in the other assays mentioned above, because H 2O 2 was added externally in these assays. In conclusion, because of this inhibitory effect on the respiratory burst activity of PMNL, the elevated blood level of butyric acid after parturition in high yielding cows may be, in part, responsible for the higher susceptibility to local and systemic infections during the postpartum period and during subclinical and clinical ketosis.