Relationship of Cell Surface to Metabolism

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Abstract
There is little or no direct absorption of glucose phosphate from the small intestine of the rat. However, glucose-1-phosphate is very rapidly hydrolyzed in intestinal loops at a max. rate of 3.6 m[image]/hr. for the entire small intestine. Orthophosphate can be almost completely recovered in the loop but glucose can be only partially recovered for some is absorbed. The rate of hydrolysis of glucose-1-phosphate is about the same in all parts of the small intestine and is the same in excised loops as in "in vivo" loops. In contrast the absorption of glucose is decreased along the length of the intestine from the stomach to colon, and is markedly reduced in excised loops. Eight other phosphate compounds were tested and all were hydrolyzed to some extent in the intestinal loops. When glucose-1-phosphate with P32 incorporated is hydrolyzed, there is no interchange of labeled P with the phosphate of the intestinal cells, indicating that the hydrolysis is not taking place in the interior of the cells. Phosphatase is not secreted into the loop under the conditions of these expts. for the phosphatases apparently are bound on the surface of the intestinal cells.