HIGH SODIUM-INTAKE INCREASES THE URINARY-EXCRETION OF L-3,4-DIHYDROXYPHENYLALANINE BUT FAILS TO ALTER THE URINARY-EXCRETION OF DOPAMINE ANDAMINE METABOLITES IN WISTAR RATS

1. The present study has examined the daily urinary excretion of L-DOP A, dopamine and its metabolites (DOPAC, 3-MT and HVA) during normal sa lt (NS) and high salt (HS) diets. 2. Daily urinary excretion of L-DOPA , DA, DOPAC, 3-MT and HVA during the 4-day period of NS diet averaged, respectively, 7.6+/-0.4, 71+/-5, 217+/-22, 570+/-90 and 1217+/-110 nm ol/kg/day. The slight increase in the urinary excretion of DA, DOPAC a nd 3-MT (16% to 42% increase), when rats were fed a HS diet, did not a chieve statistical significance. 3. In contrast, the urinary levels of L-DOPA during the HS diet period (11+/-1 nmol/kg/day) were found to b e significantly higher than during the NS diet period; the maximal inc rease in the urinary excretion of L-DOPA (93% increase) was observed i n the first day and then a progressive decline was observed towards th e end of the HS intake period. 4. During the first 5 days of the HS in take period, the urine output of noradrenaline (NA) was found to incre ase (27% to 83%) and then to progressively decline to baseline values (13.5+/-0.7 nmol/kg/day). 5. Urinary excretion of adrenaline (AD) duri ng the HS intake period was found to increase (72% to 146%); the mean daily urinary excretion of AD during the NS diet period averaged 2.5+/ -0.4 nmol/kg/day. NA and DA contents in the kidney of rats on a NS die t were not significantly different from that of rats in a HS diet. 6. It is concluded that long-term HS intake in Wistar rats fails to chang e the urinary excretion of DA and of its metabolites (DOPAC, 3-MT and HVA). Furthermore, the discrepant profile in the urinary excretion of L-DOPA and DA during HS intake might be related to a reduction in the tubular uptake of the amino acid, rather than reflecting a decrease in its decarboxylation. Copyright (C) 1996 Elsevier Science Inc.