Plasma dopamine, urinary dopamine and their metabolites in chronic renal failure

To assess the clinical features of the dopamine (DA) metabolism in chronic renal failure patients (CRF), measurements were made of the plasma DA, norepinephrine (NE), epinephrine (EN) and their urinary metabolites in 6 healthy controls and 13 CRF patients before and after administration of oral DA (KW-3160, Kyowa Hakko Kogyo Co., Ltd.). The data obtained, including that for impaired DA metabolites in the patients with chronic renal failure, can be summarized as follows: I) Synthesis: In the plasma, the DA, NE and EN levels were not significantly different in the CRF patients as compared to those in normal controls, but the excretions of urinary free DA, NE and EN were markedly lower, and the free and conjugated DA, NE and EN levels were significantly decreased in the CRF patients after DA administration. These findings indicate that the plasma dopamine beta-hydroxylase activity is inhibited in CRF patients. II) Degradation: Increased levels of urinary free and conjugated 3,4-dihydroxy phenylacetic acid (DOPAC) and decreased levels of urinary conjugated homovanillic acid (HVA) were observed, indicating that the monoamine oxidase (MAO) activity in the plasma is possibly augmented, and the catecholamine O-methyl transferase (COMT) activity inhibited, in uremic patients. III) Excretion: The urinary excretions of free DOPAC, HVA, NE and vanillylmandelic acid (VMA) and of conjugated DA and DOPAC were significantly correlated with the creatinine clearance. These data suggest that the excretion of urinary DA and part of its metabolites may be regulated by the renal function.