The intestinal absorption of glucose

Abstract

It is generally agreed that glucose is absorbed from the mammalian intestine by an active process, but the details of this are still not known with any certainty. It 10-20 mg/100 ml. higher than in the arterial blood when a solution of 13-5 % glucose was present in the intestine. With a concentration in the intestine 100 times that in the blood an enormous gradient for diffusion existed, and from such an experiment no conclusions could be drawn as to whether the glucose appearing in the mesenteric blood was actively or passively transported. Recently, Hestrin-Lerner & Shapiro (1953, 1954) claimed that glucose was absorbed in a form which was neither glucose nor lactic acid, but this claim could not be substantiated in experiments in vitro by Newey, Smyth & Whaler (1955). The present work deals with a quantitative investigation of the fate of glucose absorbed from the intestine in vivo, and with an attempt to determine in what form the absorbed glucose appears in the mesenteric blood.In preliminary experiments a solution to the problem was sought by chemical estimation of the glucose and lactic acid in the intestinal lumen and in the blood. The glucose disappearing from the intestine was measured, and at the same time the change in the glucose and lactic acid contents of the blood passing through the intestine was determined. These attempts proved unsuccessful because of the fluctuations not only of glucose but also of lactic acid in the arterial blood during the experiment. Other difficulties were the relatively large amounts of glucose brought to the intestine in the arterial 37-2

Analysis of the inhibitory effect of biguanides on glucose absorption: Inhibition of active sugar transport

“…of incubation 80.8% of the radioactivity of tdC.D-glucose could be recovered as D-glucose. This corresponds to reports in the literature for rat intestine where D-glucose can be metabolized to quite an extent [3]. In the presence of phenethylbiguanide (10-2M) uptake of l~C-D-glucose was inhibited by 64.4%, none of which could be found as 'true' D-glucose in the tissue.…”

“…As metabolism of D-glucose occurs during the course of transport even in the absence of phenethyl. biguanide [3] (Fig. l), D-glucose is not a suitable compound ~o measure transport.…”

A preparation of perfused small intestine for the study of absorption in amphibia

“…At this lumina] concentration the rate of metabolism was 16 % of the rate of net glucose absorption from the intestinal lumen. The recovery of absorbed glucose in the vascular perfusate (84 %) thus compared favourably with recovery in vivo with mammalian intestine (Atkinson, Parsons & Smyth, 1957;Kiyasu, Katz & Chaikoff, 1956).…”

Calcium and Strontium in Rat Small Intestine Their Fluxes and Their Effect on Na Flux

“…The data in Table V permit us to calculate that the diffusible Ca in the blood stream would have to rise to 9.4 rnM for the influx to be passive according to the criterion of Ussing. It can be shown that this value is unreasonable on the basis of the measured fluxes, if the intestinal blood flow data of Atkinson, Parsons, and Smyth (14) in dog may be taken as applicable to the rat2 O n this basis, we might expect a diffusible Ca concentration in the blood stream of only 2.1 raM, a rise of only 0.5 mM above the normal diffusible Ca concentration. Thus, it seems unlikely that the extra influx of Ca into the intestine can be ascribed to a local increase of Ca in the plasma.…”