Studies on Inorganic Phosphate, Inorganic Pyrophosphatase, and Alkaline Nonspecific Phosphomonoesterase Levels in the Gastrointestinal Tract of the Rat.

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Abstract
The concentrations of free inorganic phosphate in acid extracts of the mucosae of different segments of the small intestine of the male rat was studied before and after feeding, and of the activities of inorganic pyrophosphatase and alkaline nonspecific phosphomonoesterase in total aqueous homogenates of the mucosae of various segments of the gastrointestinal tract and the liver. The level of free inorganic mucosal phosphate was found to be roughly constant (about 10 [mu]mole/g of dry weight) in the small intestine and feeding had no effect on it. The activity of inorganic pyrophosphatase was maximal at the oral end of the small intestine and decreased almost linearly along the intestine to about a 4th of the activity at the oral end. The other parts of the gastrointestinal canal resembled the aboral part of the intestine in their enzyme activity. The enzyme activity was lower also in the liver than at the oral end of the intestine. The activity of alkaline nonspecific phosphomonoesterase was maximal at the oral end of the intestine and declined rapidly to about one tenth in the middle of the intestine. The enzyme activity was of the same magnitude in the stomach as at the aboral end of the intestine and even lower in the liver.