CHEMILUMINESCENCE KINETICS OF BLOOD AND MILK NEUTROPHILS DURING PHYSIOLOGICAL AND PATHOLOGICAL CONDITIONS OF THE BOVINE MAMMARY GLAND

摘要

Bovine blood and milk neutrophils (PMN) have a potential to produce a substantial amount of reactive oxygen species (ROS) to combat pathogens. PMN ROS production can be measured following stimulation with soluble agents, e.g. phorbol 12―myristate 13―acetate (PMA) or with particles e.g. zymosan, bacteria, latex beads. The most widely used technique to quantify PMN ROS production is chemiluminescence (CL) assay, which was first described by Allen et al. The different responsiveness of blood and milk PMN to PMA stimulation during physiological and mastitis conditions could result from differences in protein kinase C, NADPH-oxidase and myeloperoxidase (MPO) activities. As these enzyme activities reflect intra-and-extracellular reactions, changes might offer some evidence about the cow's susceptibility to mastitis. For example, the maximal animal susceptibility for clinical mastitis coincides with the minimal PMN ROS production capacity. Furthermore, the severity of coliform and endotoxin mastitis is less pronounced in animals with higher preinfected PMN CL. Therefore, the kinetics of blood and milk PMN ROS production could provide further insight on dissimilarities of first line defence mechanism during lactation cycle and mastitis.