Relation of Purified Pituitary Growth Hormone and Insulin in Regulation of Nitrogen Balance

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Abstract
In depancreatized cats given a constant supply of food and insulin, admn. of anterior pituitary growth hormone resulted in N storage equal to about half that observed in normal animals given the same dose of growth hormone. Depancreatized cats retained as much N as normal animals if the dose of insulin was increased. Without growth hormone, variations in insulin dosage which could be applied in the usual treatment range did not alter the N excretion. With insulin constant, a larger dose of growth hormone caused more retention of N than a small dose. In the absence of insulin (Hypophysectomized-depancreatized cat) growth hormone caused no retention of N. Growth hormone caused glycosuria in 2 normal cats. It increased the glycosuria of depancreatized cats on a constant dose of insulin. The glycosuria of Houssay cats was increased without a change in N excretion, in contrast to the increased N excretion produced by ACTH in the same animals. The results appear to support the following concepts, (a) Insulin is essential to the protein anabolic effect of growth hormone, (b) An increased secretion of insulin presumably occurs in response to growth hormone in normal animals, (c) This increased demand for insulin may be sufficiently great to exceed the body''s functional reserve. This is suggested by the increment in insulin needed to restore normal N retention, by the production of diabetes and by the work of others on insulin resistance, (d) Much if not all of the diabetogenic effect of growth hormone occurs in the tissues and not upon insulin itself (cf. Houssay animals), (e) Although insulin is an essential synergist, the level of growth hormone appears to play a dominant role in the regulation of N metabolism and to be independent of minor changes in the insulin supply.