Absorption, kinetics, antibody-bound and free serum determination of a 14C-labeled Escherichia coli extract after single oral administration in rats.

The bioavailability of the major fraction of a 14C-labeled Escherichia coli extract (OM-89) of high molecular mass > 30 kD (HEC) was investigated in rats after a single oral administration of a dose of 100 mg/kg b.w. The determination of radioactivity in blood and plasma showed that HEC was absorbed by the digestive tract, either in its original form or partly degraded. In plasma, the radioactivity reached a Cmax value after 4 h, equivalent to an extract concentration of 31.7 micrograms/g of plasma with an elimination half live of 33 h. High molecular weight molecules of HEC (> 30 kD) were found by radiochromatography in rat serum 4 h after administration. Immunoprecipitation in the serum showed that HEC retains intact determinants throughout the digestive and absorptive processes. It is therefore absorbed either in its original form or partly degraded. A high incorporation of radiolabel was found in liver, secretory glands (adrenals, thyroid gland, pancreas), and in lymphoid organs (spleen, mesenteric lymph nodes).