Absorption of Glucose and Methionine from the Hu- Man Intestine; the Influence of the Glucose Concentration in the Blood

The inaccessibility of the absorbing surface of the small bowel and its blood supply has made studies of intestinal absorption difficult and has left large gaps in our knowledge of the fundamental mechanisms involved and the factors influencing them. Animal experimentation has provided the basis for much of what is known (1). The desirability of obtaining similar data in the human subject has led to many ingenious methods for the measurement of absorption in man. None of these, however, has proved entirely satisfactory. Studies of systemic blood concentrations of ingested materials reflect utilization, rate of storage, excretion, and circulatory competency as well as absorption. Recent methods using the sampling of "portal" blood from anastomotic abdominal vessels in cases of portal hypertension employ as subjects patients with cirrhotic livers, in which the effects of the portal hypertension on absorptive processes, and the extent and effect of dilution of intestinal venous blood with hepatic arterial blood are unknown (24). Balance studies require elaborate supervision, are expensive, and are inapplicable to the study of absorption of sugars, due to destruction from fermentation. Various techniques using intubation of the human small bowel have provided a more direct approach to the subject (5-7). Disturbance of normal intestinal functioning has led to objections to several of these procedures (8). Nicholson and Chornock (9) seem to have devised the most physiologic of the intubation methods for the measurement of absorption. In their technique