Effects of beta-hydroxybutyric acid on bovine milk leukocytes function in vitro

The in vitro effect of different concentrations of beta-hydroxybutyric acid (betaHBA) on bovine milk leukocytes was examined. betaHBA level similar to those found in cows with clinical ketosis induced a significant inhibitory effect on the nitroblue tetrazolium reduction as a mean of assaying the metabolic integrity of macrophages after the phorbol-mirystate- acetate and opsonized zymosan stimulation. In the same way, the H2O2 production after stimulation with both soluble and particulate agents decreased significantly in 33 and 26%, respectively, compared with cells incubated without ketone bodies. This result suggests a possible fault in the microbicidal oxidative activity. The macrophage phagocytosis also decreased in cells treated with different betaHBA concentrations, in relation to that obtained from control cells. Neutrophils migration in agarose was determined, and the mean chemotactic response was higher when the cells were incubated with lower level or absence of ketone bodies. Considering the determined differences, we hypothesize that abnormally high levels of ketone bodies could produce a direct effect on leukocyte membranes. The induction of some modification on the receptor structure impairment the interaction ligand-receptor and this may be, in part, responsible for the higher susceptibility to local infections in mammary gland during subclinical and clinical ketosis.