FORMATION OF POLYMORPHONUCLEAR LEUKOCYTE ELASTASE - ALPHA(1) PROTEINASE-INHIBITOR COMPLEX AND A-ALPHA(1-21) FIBRINOPEPTIDE IN HUMAN BLOOD STIMULATED WITH THE CALCIUM IONOPHORE A23187 - A MODEL TO CHARACTERIZE INHIBITORS OF POLYMORPHONUCLEAR LEUKOCYTE ELASTASE

Incubation of human blood with the secretagogue A23187 resulted in the formation of increased plasma concentrations of polymorphonuclear leu kocyte (PMN) elastase:alpha(1) proteinase inhibitor (PMNE:alpha(1)PI) complex as well as A alpha(1-21) fibrinopeptide [A alpha(1-21)]. The f ormation of these species was both time and A23187 concentration depen dent. Using a sandwich ELISA and a radioimmunoassay, we determined the comparative potencies of several compounds to inhibit the formation o f PMNE:alpha(1)PI complexes and A alpha(1-21), respectively. L-658,758 , a substituted cephalosporin, essentially irreversible elastase inhib itor, inhibited the formation of PMNE:alpha(1)PI and A alpha(1-21) wit h IC50 values of 38 and 15 mu M, respectively. L-683,845, a monocyclic beta-lactam, was much more potent against isolated PMNE than L-658,75 8. However in this system it was approximately equivalent to L-658,758 with an IC50 of 15 mu M against both species. ICI-200,880, a competit ive slow-binding elastase inhibitor, was significantly less potent to inhibit A alpha(1-21), having an IC50 of 75 mu M, while Declaben, a re versible noncompetitive inhibitor, was inactive at concentrations as g reat as 200 mu M. We propose that evaluating inhibitors in the complex milieu of blood will provide a useful method to predict their therape utic potential in vivo.