Protein Synthesis by Rat Intestinal Mucosa: THE ROLE OF RIBONUCLEASE

Abstract

Abstract Protein synthesis in rat intestinal mucosal cells has been studied in slices and subcellular fractions. Intestinal cells incorporated 14C-l-leucine into protein at rates comparable to that of liver. However, homogenates of intestine were inactive in protein synthesis. It was found that polyribosomes could not be isolated from intestinal mucosa without the use of methods to diminish ribonuclease activity. The jejunal mucosa was found to contain more soluble ribonuclease activity than ileal mucosa. This increase in activity could be eliminated by prior ligation of the common bile duct, thereby reducing intraluminal pancreatic enzymes. Tissue slices from the jejunum incorporated less 14C-l-leucine into protein than ileal slices, and this difference appeared to be explained, at least in part, by the difference in mucosal ribonuclease activity. Ribonuclease was found to be absorbed by the intestine into the portal vein in small but nevertheless significant amounts. It is concluded that in the rat ribonuclease can be absorbed by the intact intestine, and can modify the function of intestinal cells in vitro as well as the structure and function of isolated ribosomes.