Intrarenal production of dopamine and natriuresis following DOPA and saline infusions in healthy human volunteers.

The interactions of intrarenal dopamine (DA) synthesis and natriuresis were studied in 11 healthy volunteers by giving a low and high sodium diet (LoSo, 50 mmol Na+; HiSo, 250 mmol Na+). On 2 days in both dietary phases an acute saline load was given, without or with an infusion of the DA precursor 3, 4-dihydroxyphenylalanine (DOPA) 0.15 microgram kg-1 min-1. Urinary excretion rates of sodium (UNa V), DOPA (UDOPA V), DA (UDA V) and noradrenaline (NA; UNA V), hormonal parameters, blood pressure (BP), glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured. On HiSo UDOPA V increased by 35% (P < 0.05) while UDA V remained unchanged. Only weak correlations were found between 24h UNa V and UDA V (r = 0.23) or UDOPA V (r = 0.39). On both diets and without the DOPA infusions, the saline infusions enhanced UNa V but did not increase UDA V. The DOPA infusions caused no significant change of UNa V, in spite of five- to eight-fold increases in UDA V. During LoSo the DOPA infusion only caused a slightly larger increase of UNa V after the saline infusion, when expressed as percentage change to the pre-saline UNa V (119 +/- 25% without DOPA infusion, 244 +/- 56%, P < 0.05 with DOPA infusion). On HiSo the DOPA infusion did not affect UNA V. The dietary sodium intake and the DOPA infusions did not influenced BP, GFR, or ERPF. In conclusion, dietary sodium intake or acute sodium loads did not clearly modulate UDA V.(ABSTRACT TRUNCATED AT 250 WORDS)