Comparison of superoxide production, protein kinase C and tyrosine kinase activities in neutrophils from neonatal calves and cows

Abstract

Superoxide (O 2 −) production and intracellular signal transduction of neutrophils were evaluated in five Holstein dairy calves and five lactating cows. Opsonised zymosan (OPZ)-induced O 2 − production by neutrophils from neonatal calves was significantly higher (P<0·01) than that of neutrophils of cows, whereas heat-aggregated IgG (H-agg.IgG)- and phorbol myristate acetate (PMA)-induced O 2 − production of neutrophils were significantly lower (P≤0·01) than those of cows. To clarify the functional differences of intracellular signal transduction in neutrophils between neonatal calves and cows, the activities of protein kinase C (PKC) and tyrosine phosphorylation were evaluated in OPZ-, H-agg.IgG- and PMA-stimulated neutrophils. Membrane-associated PKC activity of OPZ-stimulated neutrophils from neonatal calves was significantly higher (P<0·05) than that of cows, whereas PKC activity in membrane-associated fractions of H-agg.IgG-stimulated neutrophils from neonatal calves was significantly lower (P<0·05) than that of cows. A significant difference was not found in membrane-associated PKC activity of neutrophils stimulated with PMA between neonatal calves and cows. The amount of tyrosine phosphorylated 100 kDa protein in neutrophils from neonatal calves stimulated with OPZ, H-agg.IgG and PMA were 1926, 67·8 and 97·2 per cent of those of cows, respectively. These results indicate that complement receptor type 3 (CR3)- and Fc receptor (FcR)-mediated O 2 − producing activities of neutrophils are clearly different between neonatal calves and cows. This phenomenon may be associated with the age-related changes in intracellular signal transduction of neutrophils including PKC activity and tyrosine phosphorylation of cellular protein.