Role of the pituitary and the adrenal in the mobilization of free fatty acids and lipoproteins.

Treatment of normal rats with epinephrine in oil resulted in a rapid rise in plasma free fatty acid (FFA) levels. The return of FFA levels to normal coincided with the steeply increasing blood glucose concentration. The plasma FFA response to epinephrine was abolished by hypophysectomy or by adrenalectomy. The in vitro rate of release of FFA from the epididymal fat bodies of operated animals waa only about one-half that from fat bodies of normal animals. The in vitro rate of release of FFA from fat bodies removed 30 minutes after injection of epinephrine was two to three times as high as that in fat bodies taken from noninjected animals. The fat bodies taken from hypophysectomized and adrenalectomized animals showed stimulation by epinephrine, but the absolute rates of release were lower than those observed in fat bodies taken from intact rats. Normal rats receiving epinephrine showed highly significant elevations of serum cholesterol and phospholipid levels but no rise in triglyceride levels. The cholesterol and phospholipid responses to epinephrine were also abolished by hypophysectomy and substantially reduced by adrenalectomy. Attempts to mimic the action of epinephrine and induce an elevation of plasma lipoprotein levels by infusing sodium oleate intravenously were negative ; the amounts which could be safely infused, however, may have been inadequate. It was concluded that the pituitary and adrenal glands play an important role in the response to the lipid-mobilizing action of epinephrine, both in terms of FFA and lipoprotein responses.