STIMULATION OF BUTYRATE ABSORPTION IN THE HUMAN RECTUM IN-VIVO

Background: Models of short-chain fatty acid absorption have focused o n the stimulation of sodium absorption, an effect mainly located in th e proximal colon of man. With the present efforts to utilize butyrate enemas as a treatment of ulcerative colitis, it seemed important to as sess the transport in the rectum. Methods: Non-equilibrium dialysis of the rectum was applied by placing dialysis bags containing various el ectrolyte solutions in the rectum of volunteers for 30 min. In this pe riod changes in ion concentrations were linear with time. Net absorpti on and secretion rates were calculated from the change in fluid compos ition. Results: Sodium absorption was highest (24 +/- 8 mu mol/cm(2) h ) in the presence of chloride and lowest (16 +/- 2 mu mol/cm(2) h) in the presence of bicarbonate and butyrate. Butyrate (70 mmol/l) was abs orbed at a high rate of 7.1 +/- 2.2 mu mol/cm(2) h, independent on the presence of chloride, and was accompanied by increased bicarbonate se cretion. Butyrate absorption increased to 9.6 +/- 1.8 mu mol/cm(2) h i n sodium-free high-potassium media containing bicarbonate. Conclusion: The results show that it is possible to increase butyrate uptake by m anipulation of the electrolyte composition in the rectal lumen. Maxima l uptake occurred with an electrolyte composition that was similar to the natural rectal content. The information gathered could be useful i n designing enemas for trial in ulcerative colitis, provided the findi ngs can be confirmed in these patients.