Studies of Monosaccharide Permeability of Arterial Tissue and Intestinal Smooth Muscle; Effects of Insulin

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Abstract
The permeability of C14‐labelled D‐xylose and the accumulation of D‐glucose‐C14 were studied in rat and rabbit aorta and rabbit colon smooth muscle. C14‐labelled sucrose and sorbitol were used to estimate the extracellular space. In rabbit colon the distribution of sucrose‐C14 and sorbitol‐C14 reached an equilibrium after 30 min and were confined to about 40–50% of wet tissue weight. The initial distribution of D‐xylose‐C14 and D‐glucose‐C14 was the same as that of sucrose‐C14 and sorbitol‐C14 but reached no equilibrium after 30 min, instead there was a gradual increase which persisted for at least 150 min. The same results were obtained in rat and rabbit aorta. These findings indicate that D‐glucose and D‐xylose can penetrate the smooth muscle cell membrane, while sorbitol and sucrose are confined to the extracellular space. When rabbit colon was incubated for 60–180 min in D‐glucose‐C14 there was a continuous rise of tissue activity which exceeded a distribution in the extracellular space. The tissue concentration of unlabelled D‐glucose determined by an enzymatic method was constant during the same incubation times and corresponded to a distribution in the extracellular space. It seems probable therefore that the membrane permeability of D‐glucose is rate limiting for the metabolism of glucose in the smooth muscle cells.Insulin (0.1 U/ml) increased moderately the accumulation of C14‐labelled D‐glucose in rat aorta and rabbit colon and the accumulation of D‐xylose‐C14 in rabbit colon.