Utilization of 14 C-labeled E. coli by the Rat Cecum and After Force-feeding 1

Abstract

Summary

Radioactive E. coli produced by means of adding glucose-U-¹⁴C into the culture medium was placed into the cecum of six adult male rats. The rats were then placed in metabolic chambers for the collection of respiratory CO₂. At the end of 4 hr, almost 5% of the dose appeared as CO₂ indicating that the E. coli were digested in and absorbed from the cecum. Further evidence that this occurred came from the finding that 30.5% of the dose appeared in the carcass of the rats killed at the end of the metabolic CO₂ collection period. About 70% of the dose remained in the cecum and large intestine at this time which is the portion not absorbed. Another six comparable rats were gavaged with the radioactive E. coli. Carcass and fecal analyses and measurements of activities in the gastrointestinal contents indicate that 24 hr after gavage, the rat retained 43.5% of the gavaged dose. They did not digest 7.3% (fecal activity) plus 4.2% (remaining in the gastrointestinal tract) for a total of 11.5%. Thus, the digestion coefficient for E. coli is 88.5% and net utilization is 83.8% since 4.7% of the gavaged dose appeared in the urine in 24 hr. Fractionation of carcass samples revealed that the rat utilized the products obtained from the digestion or degradation of the radioactive E. coli force-fed or placed in the cecum for the formation of lipids, protein and other carbon-containing materials.