Comparison of plasma endotoxin levels in germ-free, SPF and conventional laboratory animals (mice and rats)

Plasma endotoxin levels were examined in laboratory mice and rats sustained under germ-free (GF), SPF and conventional (CV) conditions. The values were 1.72 (GF mouse), 2.67 (SPF mouse), 2.44 (CV mouse), 2.05 (GF rat), 2.56 (SPF rat), and 3.13 pg/ml (CV rat). The GF animals showed the lowest levels, followed by SPF and CV animals, in that order. When SPF animals were transferred into the conventional condition (conventionalization), the plasma endotoxin levels changed slightly, but not significantly. The present study demonstrates that the levels of plasma endotoxin in healthy laboratory animals are relatively stable and are not affected by microbiological conditions.