Effects of fat feeding on epinephrine secretion in the rat.

Adrenal medullary activity increases with fasting, although a role for diet in the regulation of epinephrine (Epi) secretion is otherwise unknown. The current studies examined the effects of dietary fat on adrenal medullary function in male CD rats. Addition of lard to a lab chow diet (+50% of chow energy) for 4 days lowered Epi excretion by 14% (P = 0.0005). Two weeks' exposure to diet containing 33% lard (by energy) reduced urinary Epi compared with that in animals fed an isoenergetic amount of chow. Epi levels in plasma obtained by indwelling catheter from unanesthetized unrestrained rats were lower in lard-fed rats than in chow-fed controls. The plasma Epi response to intravenous administration of d-fenfluramine (4 mg/kg), however, was exaggerated in the lard-fed rats. Plasma NE levels also rose after d-fenfluramine, but responses did not differ between diet groups. Urinary Epi was also measured after exposure to other fats. Beef tallow, like lard, suppressed Epi excretion, but safflower, medium-chain triglyceride, coconut, and soybean oils did not. These results suggest that fats of animal origin, in contrast to those derived from plants, suppress adrenal medullary function, possibly via alteration in central serotonergic pathways.