The release of bradykinin in bovine mastitis.

The kinin peptides are released during inflammation and are amongst the most potent known mediators of vasodilatation, pain and oedema. Despite early reports of the presence of kinins in milk, no previous study has investigated the role of the kinin system in bovine mastitis. The present study indicated that mastitis was accompanied by raised levels of bradykinin (BK) in milk and the increased levels of BK correlated with the severity of mastitis. Raised BK levels in mastitic milk were not dependent on the presence of inflammatory cells, nor were they secondary to changes in blood levels of BK. In milk from sub-clinically inflamed quarters, BK was raised in those milks where Staphylococcus aureus (S. aureus) was isolated but not in those milks where no pathogen was isolated. Increasing S. aureus artificially, also caused an increase in the milk BK. Increases in milk BK were not restricted only to the mastitic quarters of the udder. In udders in which mastitis was detected in one or more quarters, BK increases were also detected in the apparently uninvolved quarters.