Three experiments were performed in the course of developing a suitable design to study the mineral-phosphatase interaction in the young chick. Commercial and semi-purified diets of varying Ca and P content were utilized in attempts to alter the intestinal alkaline phosphatase (AP) activity. Excess Ca (2.5%) in a commercial chick starter ration caused an initial decrease in AP (after 1 to 3 days) and an elevation of the enzyme (at 10 days) compared to control (1.0% Ca). On day 10 the enzyme was positively correlated with intestinal and plasma Ca and inversely correlated with plasma Zn. A low P semi-purified diet did not alter intestinal AP compared to the same diet containing adequate P (during 6 days). There appears to be developmental alterations in the mineral-phosphatase relationships during the first two weeks of life in the chick.
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.
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