Radioisotope techniques for the study of protein absorption

The earliest attempt to use a labelled protein for the study of intestinal absorption was made in 1952. Researchers were able to show that an oral dose of I131-labelled casein was not absorbed as satisfactorily by patients with fibrocystic disease of the pancreas as by normal subjects. Their method basically consisted of feeding I131-labelled casein with a load of inactive protein and measuring the amount of unabsorbed radioactivity appearing in the faeces. This method was also used in patients with other pancreatic disorders in whom protein malabsorption was also demonstrated. However, this method did not show any malabsorption of protein in patients with coeliac disease, who are known to have a high faecal nitrogen similar to that found in pancreatic disease. One possible cause of this discrepancy could be deiodination of the labelled protein in the lumen of the bowel. To overcome this difficulty, H3-labelled albumin has recently been used to measure absorption in patients with intestinal disease. 2 figs, 1 tab