ASPIRIN CHANGES THE SECRETION RATE AND AMINO-ACID-COMPOSITION OF HUMAN SMALL-INTESTINAL MUCIN IN SUBJECTS WITH ILEAL CONDUITS

The effect of aspirin on the rate of secretion and amino acid composit ion of human ileal mucin was studied using subjects with ileal conduit s as a model system in which mucin secreted from the ileal conduit tis sue is flushed out in the urine and can be measured and analysed. Aspi rin (600 mg per day, administered orally) increased the daily mucin ou tput by 37-104% in subjects by days 3 or 4, but thereafter the mucin o utput declined to below the baseline level by day 10. Mucin samples, p urified from the ileal conduit urine during the control period and dur ing aspirin administration, were compared. There were no discernible c hanges in the degree of polymerisation or the density, but during aspi rin administration the amino acid composition was Significantly change d, and in particular threonine and proline were enriched. One possible explanation, consistent with the compositional analyses, is that the N- and C-terminal regions of the mucin subunits have been cleaved off and lost during aspirin administration. The observed changes in mucin secretion may have implications for the mechanism of the toxic effects of aspirin on the small intestine by altering the barrier properties of the mucus layer.