Differential secretion of plasminogen activator activity by postsurgical activated macrophages

Macrophage functions during postsurgical tissue repair include secretion of neutral proteases like plasminogen activator. Accordingly, we studied the differential secretion of plasminogen activator by postsurgical macrophages. Rabbits underwent resection and reanastomosis of their small bowel (three rabbits/time group). Postoperatively (up to 28 days), they underwent a second laparotomy for collection of ascites cells by lavage. Cells were incubated with culture medium containing 10% acid-treated fetal calf serum. After 2 days, the medium was removed (1-2 days media, M1) and replaced for 2 more days (3-4 days media, M2). Plasminogen activator activity of the medium (M1 and M2) was determined using a modified indirect solid-phase radioassay. The specific plasminogen activator activity (plasminogen-dependent-plasminogen-independent activator activity) in M1 was 43 mPU/10(6) cells in nonsurgical control rabbits. Exudative cells on Day 1 had less activity than control, and by Day 5, the activity significantly increased to 290% of control levels, reaching peak value on Day 14 (360%). The specific plasminogen activator activity in M2 was 310 mPU/10(6) cells in nonsurgical control media. Exudative cells on Day 1 had less activity than control, while, on Days 3-7, they were the same as control. By day 10, specific activity significantly increased to peak levels 188% of control and then gradually decreased. Since a marked increase in the number of macrophages parallels the increase in these metabolic activities through postsurgical Day 10, postsurgical activated macrophages appear to play an important role in peritoneal healing.