Participation of macrophages in chloramphenicol-potentiated carrageenin-induced peritonitis in rats.

1. We investigated the possible potentiating effect of chloramphenicol succinate (30 mg/kg, every 12 h for 4 days, ip) on the response of polymorphonuclear neutrophils to carrageenin (150 micrograms, ip) or dextran (100 micrograms, ip) in the peritoneal cavity of male Wistar rats (180-230 g; N = 12 in each group). 2. Chloramphenicol potentiated the cell migration induced by carrageenin (35%) but not that induced by dextran. Previous macrophage depletion in the peritoneal cavity by washing with sterile saline abolished the cell response, whereas a previous thioglycollate-induced increase in macrophage numbers enhanced the potentiating effect (60%). 3. These results suggest that the potentiating effect on polymorphonuclear neutrophil migration induced by chloramphenicol may be related to chemotactic factors released by macrophages.