ABSORPTION OF RADIOACTIVE SODIUM FROM THE INTESTINAL TRACT OF MAN. I. EFFECT OF INTESTINAL MOTILITY. II. EFFECT OF AN ORGANOMERCURIAL*†

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Abstract
The quantitative characteristics of normal Na absorption, i.e., unidirectional transfer of Na ions from lumen to blood, were studied by integrating the arterial appearance of Na24 after jejunal administration with the arterial disappearance of Na22 following intravenous administration. In 22 control tests a mean of 62% of the administered dose was absorbed in 5 minutes; a mean of 93% was absorbed in 12 minutes. Arterial concentration curves of Na24 during the first 8 minutes were closely correlated with calculated absorption curves during this period. When calculated in terms of amount of Na24 remaining in the intestinal lumen, transfer of Na24 to arterial blood proceeded at an exponential rate. In 9 patients, repeat control tests of intestinal absorption of Na24 under identical conditions indicated a high degree of reproducibility. The technique of using a patient as his own control was useful in the present studies on the effect of motility and organomercurial administration upon Na transport from the intestinal lumen to arterial blood. Intestinal motility as reflected by jejunal intraluminal pressure was simultaneously recorded in 15 control tests of Na24 absorption. There was some correlation between amount absorbed and amount of motor activity present. However, normal absorption occurred in several patients at a time when little motor activity was present. Intestinal motility probably does not play a critical role in absorption of isotopic Na from an isotonic saline solution in the normal small bowel. The unidirectional transfer of Na from intestinal lumen to arterial blood was significantly decreased after propantheline administration in 8 patients. This reduction in absorption was not prevented in 6 additional patients who received propantheline and had artificial spread of the Na24 over 3 feet of jejunal mucosal surface. These findings suggest that the inhibition of intestinal motility which occurs after an administration of an anti-cholinergic agent may not be primarily responsible for decreased absorption. The effect of an organomercurial, mercaptomerin, on intestinal absorption of Na24 was studied in 11 convalescent patients. No effect on unidirectional transport of Na from intestinal lumen to arterial blood was present at a time when a mercurial effect on the kidney was observed.