THE EFFECT OF HYPOPHYSECTOMY, ADRENALECTOMY AND OF ACTH ADMINISTRATION ON THE PHOSPHORUS METABOLISM OF RATS1

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Abstract
Using p32 as a tracer, the authors compared the turnover of inorganic phosphate between plasma and tissues in normal rats with that of animals which were adrenalectomized, hypophysectomized, or hypophysecto-mized and treated with adrenocorticotrophic hormone. Hypophysectomy markedly reduced the rate of turnover of inorganic phosphate between the cells and the extracellular fluids of all the tissues measured. It did not significantly affect the concn. in these tissues, however, even though the plasma level was reduced by 18%. Adrenalectomy 24 hrs. before the injn. of the isotope did not significantly affect the turnover of P in any tissue except the muscle. Injn. of ACTH into hypophysectomized rats increased the rate of turnover in all of the tissues studied. It restored the rate to normal in all tissues except muscle and brain. Plasma phosphate was further reduced, however, apprently due to retention of water. Apparently the systems involved in the transfer of phosphate across cell boundaries are under the control of ACTH; whether this is direct or via the adrenals is not clear. The regulation of the plasma phosphate level, however, depends on some other pituitary factor, probably the growth hormone.