The plasma free fatty acid rebound induced by nicotinic acid.

The time course of the nicotinic acid-induced changes in levels of plasma free fatty acids (FFA) was examined. The plasma FFA response of fasted dogs to graded doses of nicotinic acid was shown to be biphasic: an initial depression of the level of plasma FFA was followed by a rebound elevation to supernormal levels. FFA rebound was not seen after the administration of the nicotinic acid homologue, pyridylacetic acid, or a variety of nicotinic acid metabolities. A similar pattern of FFA response was observed in fasted, normal rats. Adrenalectomy did not abolish the secondary elevation of FFA but did cause a somewhat delayed response. Hypophysectomy modified the time course of the response-the initial FFA decrease was prolonged-and the intensity of the FFA rebound was diminished. No rebound was observed in hypophysectomized, adrenalectomized rats. In normal rats, nicotinic acid caused a significant rise in the level of plasma corticosterone. A normal rebound pattern was observed in thyroidectomized rats. Reserpine, administered on a schedule designed to deplete catecholamine stores, altered the time course of plasma FFA changes only slightly. The results indicate that both the pituitary and adrenal functions are required for the expression of the rebound phenomenon after nicotinic acid administration.