Difference in the inductions of duodenal alkaline phosphatase by casein feeding and by starch feeding

Feeding of starch or casein to rats that had been starved for 4 days resulted in marked increase in duodenal alkaline phosphatase activity in a few hours. In rats with a duodenal blind loop, the enzyme was induced by feeding starch, but not casein. Conditions leading to hyperglycemia, such as an intragastric administration and an intravenous infusion of glucose, induced duodenal alkaline phosphatase to the same extent and in the same period as starch feeding. Subcutaneous injection of insulin alone did not induce the enzyme. In chemically sympathectomized rats, the enzyme was induced by starch feeding. In vagotomized or hexamethonium-treated rats, the enzyme was not induced by starch feeding or intragastric administration of glucose solution. On the contrary, subcutaneous injection of carbachol alone induced the enzyme. These results suggest that stimulation of the parasympathetic nervous system via hyperglycemia is important for induction of duodenal alkaline phosphatase by starch feeding. The mechanism of enzyme induction by casein feeding is still unknown.