COMPARISON OF SUPEROXIDE PRODUCTION, PROTEIN-KINASE-C AND TYROSINE KINASE-ACTIVITIES IN NEUTROPHILS FROM NEONATAL CALVES AND COWS

Superoxide (O-2(-)) production and intracellular signal transduction o f neutrophils were evaluated in five Holstein dairy calves and five la ctating cows. Opsonised zymosan (OPZ)-induced O-2(-) production by neu trophils from neonatal calves was significantly higher (P<0.01) than t hat of neutrophils of cows, whereas heat-aggregated IgG (H-agg.IgG)- a nd phorbol myristate acetate (PMA)induced O-2 production of neutrophil s were significantly lower (P less than or equal to 0.01) than those o f cows. To clarify the functional differences of intracellular signal transduction in neutrophils between neonatal calves and cows, the acti vities of protein kinase C (PKC) and tyrosine phosphorylation were eva luated in OPZ-, H-agg.IgG- and PMA-stimulated neutrophils. Membrane-as sociated PKC activity of OPZ-stimulated neutrophils from neonatal calv es was significantly higher (P<0.05) than that of cows, whereas PKC ac tivity in membrane-associated fractions of H-agg.IgG-stimulated neutro phils 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 calv es and cows. The amount of tyrosine phosphorylated 100 kDa protein in neutrophils from neonatal calves stimulated with OPZ, H-agg.IgG and PM A were 192.6, 67.8 and 97.2 per cent of those of cows, respectively. T hese results indicate that complement receptor type 3 (CR3)- and Fc re ceptor (FcR)-mediated O-2 producing activities of neutrophils are clea rly different between neonatal calves and cows. This phenomenon may be associated with the age-related changes in intracellular signal trans duction of neutrophils including PKC activity and tyrosine phosphoryla tion of cellular protein.