Acid-stable protease inhibitor in chronic phase of carrageenin-induced inflammation in rats.

The activity and kinetics of acid-stable protease inhibitor (ASPI) were investigated in the chronic phase of carrageenin-induced inflammation in rats. The ASPI activity was 19.6 +/- 3.1 units/ml in the plasma and 15.4 +/- 2.1 units/ml in the inflammatory exudate. The plasma value was significantly higher than that of the control (11.6 +/- 1.3 units/ml). A kinetics study was performed using purified and radiolabeled rat plasma ASPI, whose NH2-terminal amino acid sequence was Ala-Val-Leu-Pro-Gln-Glu-Asn-Glu-Gly-X-Gly-Ser-Glu-Pro-Leu-Ile-Thr-Gly-Th r-Leu- Lys-Lys-Glu-Asp-Ser-Asn-Gln-Leu-Lys-Tyr-Ser-Glu-Gly-Pro. The half-life of the distributive phase was 4.3 +/- 0.4 min and that of the postdistributive phase (biological half-life) was 42.2 +/- 9.2 min in inflammation. There was no significant difference compared with the values in the control (3.9 +/- 0.4 min and 40.7 +/- 6.5 min, respectively). It appeared that the increase in ASPI in inflammation was not due to prolonged excretion of the inhibitor but to an increased production of it, and ASPI was rapidly distributed to the fluids and tissues.