Assay in mice for minute amounts of endotoxin by pre-administration of lead acetate.

The enhancing effect of pre-administration of lead acetate on the body-weight decrease due to endotoxin was studied in mice for the purpose of developing a method for determination of minute amounts of endotoxin. By adoption of the body-weight ratio on the first day after endotoxin administration (BWR1) as a response, the linear regression lines of the dose-response were demonstrated over a wide range of log doses of several different endotoxin preparations tested. By use of these linear regression equations experimentally obtained, the minimum detectable dose was calculated. The minimum detectable dose was defined as a dose of an endotoxin preparation producing a mean body-weight response statistically distinguishable from that of the control. The doses obtained were mostly in nanogram order. The magnitude of the enhancement brought about by the lead treatment was estimated at about 40 to 100 times.