Pulse-chase analysis of PAI-1 in UT-7/OR, UT-7/TPO, and HUVEC. UT-7/OR, UT-7/TPO, and HUVEC were incubated for 60 minutes in methionine-free medium and then pulse labeled with³⁵S-methionine for 15 minutes, followed by a chase with excess of unlabeled methionine for the indicated period. Cells and media were harvested at appropriate intervals, and PAI-1 was immunoprecipitated from each sample with mouse antihuman PAI-1 MoAb (JTI-3 and JTI-4) or normal mouse IgG. Subsequently, they were subjected to SDS-polyacrylamide gel electrophoresis (10% separating gels) and autoradiography.