The role of the Na, K-ATPase inhibitor in renal sodium handling in patients with essential hypertension

The present study aimed to elucidate the role of Na, K-ATPase inhibitor in renal sodium metabolism in essential hypertension. Mean arterial pressure(MAP), heart rate(HR), urine volume(UV), urinary excretion of sodium(UNaV), endogenous creatinine clearance(Ccr), fractional excretion of sodium (FENa), plasma renin activity(PRA) plasma aldosterone concentration(PAC), plasma noradrenaline concentration (PNA) and urinary excretion of noradrenaline (UNA) were measured before and after intravenous injection of ouabain (0.1mg/m2·BSA) in 12 normotensive (NT) and 22 mild-to-moderate essential hypertensive subjects (EHT). Following ouabain injection, UV, UNaV FENa significantly increased, but PRA decreased, in both NT and EHT. MAP, HR, Ccr, PNA, and UNA did not change significantly in either group. On the other hand, a significant decrease in PAC was observed in NT, but not in EHT. The changes of UNaV and FENa were significantly attenuated in EHT as compared to NT. No significant difference in change of MAP, HR, UV, Ccr, PNA, UNA, or PRA was demonstrated between NT and EHT. A significantly positive correlation was found between ΔUNaV and ΔFENa in both NT and EHT, while no significant correlation was observed between ΔUNaV and ΔMAP, ΔUV, ΔCcr, ΔPRA, ΔPAC, ΔPNA and ΔUNA in either group. These results suggest that 1) Na, K-ATPase inhibitor clearly augments natriuresis by suppression of sodium reabsorption in renal tubules, 2) since this augmentation was attenuated, there is an elevation of endogenous Na, K-ATPase inhibitor(s) should be considered in EHT, and 3) an increase of the inhibitor might participate to the hypertensive mechanism in EHT.