EFFECTS OF PURIFIED PITUITARY PREPARATIONS ON THE NONPROTEIN NITROGEN CONSTITUENTS OF BLOOD

Abstract

Purified pituitary hormones were investigated regarding their ability to decrease blood and tissue nonprotein-N constituents within a 4 hr. test period. Urea, the main component of the blood nonprotein-N, was decreased only by thyrotrophic hormone and not by growth hormone, as is generally believed. Both thyrotrophic and growth hormones lowered blood amino acids, the former more effectively than the latter. The action of thyrotrophic hormone on blood and tissue urea could be reproduced also by the adm. of thyroxin and thus is probably mediated by the thyroid gland. The action of thyrotrophic hormone on blood aminq-acids was not given by thyroxin. In thyroidectomized animals thyrotrophic hormone was still effective in lowering blood amino acids, while its action on blood urea was doubtful. The high blood and tissue nonprotein N and urea of hypophysectomized animals was lowered markedly by both thyrotrophic hormone and thyroxin, the former but not the latter also affecting blood amino acids. These findings are tentatively interpreted as indicating that thyrotrophic hormone lowers blood urea directly as well as through stimulation of the thyroid gland, while controlling the amino acid level only by a direct action. Evidence is adduced showing that the observed decrease in blood urea is not due to increased excretion, nor to hemodilution, and therefore is probably caused by a decreased production of urea in the liver.