PLASMA-DERIVED PROTEASE INHIBITORS IN BOVINE-MILK

Seven plasma-derived inhibitors, alpha(2)-macroglobulin, alpha(2)-antiplasmin, antithrombin III, C1-inhibitor, inter-alpha-trypsin inhibitor, bovine plasma elastase inhibitor (EI) and bovine plasma trypsin inhibitor (TI), have been identified in bovine colostrum and milk by western blot analysis and enzyme-linked immunosorbent assay. Apart from individual concentration differences, significantly different levels were found in colostrum, and in milk from early, mid and late lactation. It is suggested that plasma-derived inhibitors are present in milk as a result of regulatory processes connected with mammary gland development and gradual involution. EI and TI might have additional functions as inhibitors of polymorphonuclear elastase and plasmin, respectively.