Urinary dopamine and sodium excretion in spontaneously hypertensive rats

We measured urinary dopamine in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) before (days 0-6) and during high-salt diet, in the absence (days 6-10) and presence (days 10-14) of added L-dopa (2 mg/kg/day by gavage). Urinary excretion of sodium (UNaV) increased 20-fold during intake of chow containing 8% NaCl in both strains. Systolic blood pressure (SBP) of SHR increased slightly (9 +/- 4 mmHg; p < 0.05) on the high-salt diet, whereas SBP did not change in WKY. Urinary dopamine excretion was not different between strains in the basal state, and was as great or greater in SHR than WKY during high-salt intake with and without added L-dopa. SBP was unaffected by L-dopa administration and UNaV did not increase or differ between strains despite higher urinary dopamine excretion in SHR. We conclude that renal dopamine formation in vivo is not diminished in SHR, compared with WKY, on normal or high-salt diets, and that elevation of renal dopamine formation secondary to L-dopa administration is not associated with reductions in SBP or altered UNaV in these rats.