The Significance of Bile Acids and Aldosterone for the Electrical Hyperpolarization of Human Rectum in Obese Patients Treated with Intestinal Bypass Operation

Abstract

Rask-Madsen, J., Bruusgaard, A., Munck, O., Nielsen, M. D. & Worning, H. The significance of bile acids and aldosterone for the electrical hyperpolarization of human rectum in obese patients treated with intestinal bypass operation. Scand. J. Gastroent. 1974, 9, 417–426.

In an effort to clarify the mechanism of rectal hyperpolarization in shunt-operated patients, the effects of jejunoileal bypass on the rectal potential difference (PD) and the transepithelial transport of electrolytes and water in the rectum and the colon were investigated in morbidly obese patients. The transport rates of electrolytes and water were measured before and after operation by in vivo dialysis of rectal fluids, and by steady-state perfusion of whole colon. Furthermore, plasma aldosterone and renin were measured radioimmunochemically, simultaneously with exchangeable sodium and total body potassium, to evaluate whether a state of secondary hyperaldosteronism due to electrolyte derangement existed postoperatively. Since di- and trihydroxy bile salts are known to interfere with colonic ion transport, a semi-quantitative determination of faecal bile salts was carried out after chromatographic separation. A significant increase in PD was noted postoperatively (from -45 mV ± 2 to -64 mV ± 2). The mucosa to serosa flux of sodium and net transport rates of chloride and water also increased significantly when the physicochemical environments in the rectal lumen were unaffected by the procedures of measurement. On the contrary, normal values were obtained when the colon was perfused with isotonic saline. Plasma aldosterone and plasma renin decreased postoperatively in accordance with the findings of potassium depletion. A marked decrease in the concentrations of secondary bile salts (deoxycholic acid (DC), and lithocholic acid (LiC)) was observed too. It is, therefore, proposed that the hyperpolarization and the alterations in transepithelial transport of salt and water in shunt-operated patients are not the result of mineralocorticoid stimulation, but are probably due to disappearance of dihydroxy bile salts from the colonic lumen.

Key-words::

• Absorption
• aldosterone
• bile acids
• colon
• electrolytes
• intestinal shunt operation
• membrane potentials
• obesity
• rectum