Plasma Radioactivity after Rectal Instillation of Radioiodine-Labelled Human Albumin in Normal Subjects and in Patients with Ulcerative Colitis

Abstract

The permeability of the rectosigmoid mucosa was studied by following the increase of radioactivity in plasma specimens after rectal instillation of radioiodine-labelled human albumin. In seven control subjects, 1.3 per cent ± 0.7 per cent (S.E.M.) of the instilled radioactivity was found in one litre plasma after four hours, out of which 33 per cent ± 7 per cent (S.E.M.) was not dialysable to tap water by using cellulose tubings with an average pore diameter of 48 Å but precipitable with trichloride acetic acid 10% w/v. In seven patients with ulcerative colitis an absorption was demonstrated which differed only insignificantly from the values mentioned. Thus there are no grounds for assuming that a colon mucosa membrane of abnormal permeability to macromolecules plays a part in the pathogenesis of ulcerative colitis. The total excretion of radioactivity in the urine after 24 hours amounted in five cases to an average of 31 per cent of the rectally instilled dose, out of which on average eight per cent was precipitable with trichloride acetic acid 10% w/v. It is assumed that the non-dialysable fraction of the plasma radioactivity was attached to peptides liberated from the instilled albumin in the rectosigmoid.

Key-words:

• Colon
• rectum
• sigmoid colon
• intestinal absorption
• immunology
• serum albumin, radioiodinated
• peptides
• colitis, ulcerative