Clearance of histamine from the peritoneal cavity of rats

To study the clearance of histamine from the peritoneal cavity of rats, histamine was either injected i.p. or released locally by the injection of compound 48/80. At various intervals peritoneal fluid was removed and analysed for histamine concentration by a fluorometric assay. Exogenous and endogenous histamine were cleared from the peritoneal cavity at the same rate with a half life of 20 minutes. The rate was not altered by different histamine concentrations, by injection of heparin, and by the removal of peritoneal leukocytes. Repeated injections of large amounts of histamine resulted in a decreased clearance. The results suggest that histamine concentrations above the physiological level are quickly degraded. Activities of histamine as an inflammatory mediator are likely to be of short duration.