Regulation of Intestinal Alkaline Phosphatase by Dietary Phosphate

Day-old chicks were fed practical rations containing varying levels of inorganic phosphate (Pi) in an attempt to study the regulation of intestinal alkaline phosphatase by phosphate. Low dietary Pi (0.16%) increased the enzyme activity by 50% compared to adequate Pi (0.48%). The enzyme activities were significantly reversed 8 days after reversing the diets. In another experiment chicks were fed 0.16 or 0.80%) Pi for 4 weeks and killed when full-fed, or after 3 days' starvation. In the full-fed birds low dietary Pi reduced the intestinal nuclear Pi and doubled the intestinal enzyme activity. Nuclear Pi was found to be inversely correlated with alkaline phosphatase in the fed animals. No such effects were found in the starved birds.