Splenectomy in the rat. Immediate and late effects on clearance of gram-negative bacteria and on monocyte activation as expressed by thromboplastin synthesis.

Young rats (weight 190-200 g) were subjected to splenectomy or sham laparotomy and gram-negative bacteraemia was induced by caecal perforation or by injection of viable Escherichia coli intraperitoneally (10(9) bacteria) or intravenously (2 X 10(8]. Clearance of bacteria was significantly less in the splenectomized than in the sham-laparotomized rats, irrespective of the mode of microbial inoculation. Monocyte thromboplastin activity, shown to be a sensitive indicator of gram-negative bacterial presence, was heightened in the asplenic rats. When the infectious challenge was made 15 weeks postoperatively, however, no significant difference in bacterial clearance or in monocyte thromboplastin values was found between splenectomized rats and controls. Nor was increased susceptibility to gram-negative bacteria found in asplenic rats when both operation (splenectomy vs. sham laparotomy) and bacterial challenge were performed at a late age (weight 530-580 g). The postsplenectomy clearance of gram-negative bacteria thus seemed to be age-dependent.