The present study aimed to elucidate the role of renal dopaminergic and prostaglandin (PG) systems in renal uric acid metabolism in essential hypertension. Mean arterial pressure (MAP), heart rate (HR), endogenous creatinine clearance (Ccr), serum uric acid (SUA), urinary excretions of uric acid (UUAV) and sodium (UNaV), fractional excretions of uric acid (FEUA) and sodium (FENa), plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured before and after intravenous injection of a dopamine receptor antagonist, metoclopramide (MCP: 8mg/m2.BSA), or before and after a single oral administration of prostaglandin synthesis inhibitor, indomethacin (IM: 75mg), in 34 mild-to-moderate essential hypertensives (EHT).
MCP injection or acute oral administration of IM caused significant decreases of UNaV and FENa in each group, whereas MAP, HR and SUA did not change in either group. Significant decreases in Ccr, UUAV and FEUA and increases in PRA and PAC were demonstrated by MCP injection, while no significant changes in these parameters were revealed by IM administration. There was a significant positive correlation between Δ UUAV and _??_ Ccr or Δ FEUA in both groups. In addition, a close positive correlation between _??_ UUAV and _??_ UNaV as well as between Δ FEUA and _??_ FENa was found in the MCP group, but not in the IM group. On the other hand, no significant correlation was observed between _??_ UUAV and _??_ PRA or _??_ PAC in either MCP or IM administration. The decreases of UUAV and FEUA were significantly greater in MCP than in IM administration, despite similar changes in Ccr, UNaV and FENa between the two procedures.
These data suggest that the endogenous renal dopaminergic system may contribute to renal uric acid metabolism, which is rather closely related to sodium handling in essential hypertension than the prostaglandin system. Furthermore, the attenuated renal dopaminergic activity may contribute to the elevation of serum uric acid level in patients with essential hypertension.
