The uptake and transmission of protein by the gut of the neonatal rat

Abstract

The studies reported in this thesis deal with the in vivo transmission of homologous and heterologous IgG and other proteins across the proximal small intestine of the suckling rat. The uptake of these labelled macromolecules from the intestine was monitored, and the subsequent appearance of radioactive material in the serum, viscera and carcass was examined by ultrafiltration and ultracentrifugation techniques. The rate of transmission of intact IgG and IgG breakdown products across the intestinal barrier was measured with the intention of obtaining further information about the mechanisms of immunoglobulin transport. The significance of the digestive activity of the suckling rat gut to the process of antibody transmission was also assessed. This was done by gel filtration analysis of the radioactive material present in the gut wall and wash after the intraluminal injection of labelled rat IgG. The ability of trypsin inhibitor to stimulate the transmission of intact IgG was investigated, and the possibility that the IgG receptor on the surface of proximal enterocytes was trypsin sensitive was also examined. Attempts were made, using a variety of subcellular fractionation techniques, to isolate and identify the organelles involved in the receptor mediated transcellular transport of IgG