Studies with radioactive endotoxin. II. Clearance of 3H-labelled endotoxin from the blood of calves.

The clearance of (3)H-labelled Pseudomonas endotoxin from the blood was studied in a nontolerant and in an endotoxin tolerant state. Calves were rendered tolerant to the toxic effects of the endotoxin by four daily intravenous injections of endotoxin at the dose rate of 5 microg/kg body weight. Clearance of (3)H-endotoxin from the blood of nontolerant calves occurred more slowly than did clearance of (51)Cr-endotoxin and was not significantly (P<0.05) affected by the development of tolerance. The lungs and liver were the major organs involved in the clearance of (3)H-endotoxin from the blood of calves. Leukocytes and erythrocytes, but not platelets, were shown to participate in endotoxin clearance in calves. (3)H(2)O, the control substance used in calves, was not concentrated within any particular organ but rapidly equilibrated with total body water and was slowly excreted.