In vitro reduction of human blood kininogen by catecholamines.

Plasma kininogen levels were significantly reduced in normal human blood, but not in cell-free human plasma, following 10 min in vitro exposure to, in order of decreasing effectiveness, 6 microM adrenaline, noradrenaline or isopropyl-noradrenaline. Phenoxybenzamine (0.1 mM), an alpha-receptor blocking drug, and 0.5 mM aspirin, an inhibitor of prostaglandin (PG) synthesis, inhibited the action of adrenaline, whereas 0.1 mM propranolol, a beta-receptor blocker, and 0.5 mM indomethacin, another inhibitor of the formation of PG, failed to do so. The results suggest that catecholamines are able to activate cell-mediated activation of the kallikrein system in human blood and that this process can be inhibited by aspirin.