Effect of Lipoid A of the Lipopolysaccharide (LS) of E. coli on the Rat Litter in utero. ∗

Summary

The single LD₅₀ of the LS of E. coli III was 20 mg/kg. The LD₅₀ of the Lipoid A extracted from the LS was more than 200 mg/kg. The isolated Lipoid A in a single 20 mg/kg dosis on the 12th g.d. destroyed most litters of pregnant rats and was less effective than the single 2 mg/kg doses of the LS. The findings confirm Westphal's contention that the Lipoid A is the toxic factor in the LS. Lipoid A appears approximately 10 times more effective on the embryo when carried by the large LS molecule than when given in the isolated form.