Effects of Hypophysectomy, Growth Hormone and Thyroxine on Phosphatases of Tibia, Liver, Spleen and Kidneys of Rat

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Abstract
Previous observations of decreased alkaline phosphatase activity in bone and kidney and increased activity in liver following hypophysectomy, with returns toward normal control values on treatment with large amts. of anterior pituitary growth hormone prepns. have been investigated in greater detail. Treatment with physiological (small) amts. of growth hormone has now been shown to be as effective in increasing venal and tibial alkaline phosphatase activities after hypophysectomy, as the large amts. used previously, although liver alkaline phosphatase was unchanged or further increased under these conditions. Activities observed in animals 6 mos. postoperatively indicate that the effects of the ablation on tibial, renal and hepatic alkaline phosphatase persist for a long time. The enzymic response to growth hormone treatment 6 mos. after hypophysectomy was not altered. The increased hepatic and decreased renal alkaline phosphatase activities were quite significant within 5 days after hypophysectomy and are evidently an important permanent metabolic effect of hypophysectomy. Tibial alkaline phosphatase was not affected immediately after hypophysectomy in this marked manner, and does not appear to be the means by which the anterior pituitary controls osteogenesis. Treatment of hypophysectomized rats with thyroxine gave no change in body weight, food intake or hepatic alkaline phosphatase, while reducing renal and increasing tibial alkaline phosphatase activities. By contrast, in intact pair-fed animals, the same treatment resulted in precipitous weight loss, reduction in hepatic and renal alkaline phosphatase activities with little change in the activity of the alkaline phosphatase of the tibia. It has been shown that the results of hypophysectomy are independent of the manner of feeding of the normal control groups used for comparison. The results are also independent of the use of magnesium activation in the enzyme estimation. Data on renal, hepatic and spleen acid phosphatase and spleen alkaline phosphatase activities were presented in some of the experiments. The possibility of a relationship between the level of alkaline phosphatase activity and the function of the liver and kidneys is discussed.