Confluent VSMCs in 24-well tissue culture plates were incubated with either nystatin or filipin for 30 minutes, incubated with pro-uPA, washed, and assayed for plasmin generation. Data are expressed as fluorescence intensity at 20 minutes after the addition of plasminogen (±SD of triplicate determinations) and the percentage of plasmin generation compared with untreated cells. These treatments were shown to disrupt caveolae as determined by a redistribution of caveolin immunofluorescence (data not shown).