Relation of Cortisone Pretreatment to Mobilization of Lipids to Liver by Pituitary Extracts.

Abstract

Many, but not all, pituitary prepns., when injd. into intact mice at the beginning of a 7-hr. fasting period, increase the fat content of the liver. This response is completely abolished by prior adrenalectomy. No adrenal cortical steroid so far tested can of itself cause a substantial increase in the liver fat content of intact or of adrenalectomized mice, but the usual post-adrenalectomy loss of liver fat is prevented by such treatment. When pre-treated with cortisone (3.5 mg. during the 3.5 days preceding the expt.), adrenalectomized mice respond to pituitary hormone by mobilization of fat to the liver as well as, or better than, untreated intact mice. Pituitary substances (growth hormone; weakly potent ACTH), inactive in either intact or adrenalectomized mice, become effective in mobilizing fat to the liver if the animals are pre-treated with cortisone. The findings are interpreted as indicating that for the mobilization of fat to the liver at least 2 endocrine factors are required: adequate supplies of circulating adrenocortical hormone from either endogenous or exogenous sources, and a supply of the "triggering" pituitary factor. The "triggering" action of the pituitary substance is a direct one, not mediated by the adrenal cortex, since it is operative in the absence of the adrenal gland (provided adequate amts. of cortisone are admd.). The possible identity of the pituitary substance is discussed.