Studies in vitro of the passage of serum proteins across the intestinal wall of young rats

Everted ileal sacs of 18-day-old rats were used as in vitro preparations, and a modified technique for their preparation is described. These sacs remained viable and functional for at least 1 h when incubated at 37° C under aerobic conditions. Such preparations showed transport across the intestine against concentration gradients of l-histidine or of radioactive iodine and oxygen uptake was consistent over the period of the experiment. Homologous and heterologous agglutinins and 131I-labelled γ-globulins were transported from the mucosal to the serosal fluid. Gamma-globulins were transmitted from the mucosal to the serosal fluid differentially depending upon the species of origin. A part of the protein absorbed was broken down during transport and an increase in oxygen consumption of the tissues occurred during protein transport.