Experimental approach to a role of the increased T-kininogen level in carrageenin-induced pleurisy of rats.

In order to elucidate the biological role of T-kininogen, it's levels in plasma, exudate, and liver were measured by radioimmunoassay in rats following the induction of carrageenin pleurisy. T-kininogen level in the liver microsomes was increased markedly at 8-24 hr after the carrageenin injection, and its plasma level increased at 24-48 hr with a delay. Pretreatment with dexamethasone suppressed the pleural exudate accumulation almost completely, but inhibited the T-kininogen level in plasma or liver only partially. When rats were pretreated with carrageenin injection into a paw 2 days prior to intrapleural injection of carrageenin, the pretreatment did not affect the pleurisy development, even though the plasma level of T-kininogen was greatly increased. Increased level of T-kininogen correlated well with the thiol protease inhibitor activity found in the plasma and exudate. These results indicate that an increase in the T-kininogen level does not influence the exudation, but might act as an inhibitor of thiol proteases that could be released at the inflammatory site.