THE EFFECTS OF GROWTH HORMONE AND CORTICOTROPHIN UPON THE ADRENAL WEIGHT AND ADRENOCORTICAL MITOTIC ACTIVITY IN THE HYPOPHYSECTOMIZED RAT

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Abstract
SUMMARY: 1. Treatment of rats 17–24 days after hypophysectomy with pituitary growth hormone for 3 days causes a definite, although limited, increase in adrenal weight. When growth hormone and corticotrophin are given simultaneously, the increase in adrenal weight is greater than the sum of the effects with the hormones separately. The larger the dose of corticotrophin the greater the synergic effect. 2. The action of growth hormone on the adrenal is characterized by a striking stimulation of cell division with relatively little effect on adrenal weight. Corticotrophin also stimulates adrenocortical mitotic activity, but to obtain mitotic activity equivalent to that with growth hormone, doses must be given sufficient to cause a great increase in adrenal weight. This is true whether corticotrophin is injected in saline or in a beeswax/arachis oil mixture. 3. The characteristic activity of each preparation in stimulating the adrenal can be expressed in terms of a quotient, Qmw, the ratio of mitosis-stimulating activity to increase of adrenal weight in a single test. This index is effectively independent of the absolute responses. For growth hormone, Qmw is high; for biologically pure corticotrophin, it is low. Artificial mixtures of the two hormones give intermediate values of the quotient; crude corticotrophin preparations give values higher than those for purified preparations.