Differential catecholamine responses to dietary intake: Effects of macronutrients on dopamine and epinephrine excretion in the rat

Sympathetic nervous system (SNS) function responds to changes in diet in animals and humans; whether alterations in peripheral dopaminergic activity or in adrenal medullary secretion also occur with dietary manipulation is unclear. The present studies in rats demonstrate that casein supplementation of a lab chow diet raised urinary excretion of dopamine (DA) and epinephrine (E); both sucrose and lard feeding suppressed urinary DA, though only lard appeared to exert any effect on E excretion (reduction). Addition of tyrosine to the chow diet in an amount equivalent to the tyrosine content of casein increased DA output comparably to that seen in casein-fed rats, but did not reproduce the effects of casein on E excretion. Oral administration of carbidopa, an inhibitor of 3,4-dihydroxyphenylalanine (DOPA) decarboxylation in kidney reduced the DA response to casein, but chemical sympathectomy, which lowered urinary norephnephrine (NE), and adrenal denervation, which diminished E excretion, did not. Thus, the patterns of response of the peripheral dopaminergic system in kidney and of the adrenal medulla to short-term nutrient and tyrosine ingestion are distinct from those observed for the SNS and for each other, suggesting that all three peripheral catecholamine systems may be governed by separate regulatory mechanisms.