Nephron‐Specific Disruption of Nitric Oxide Synthase 3 Causes Hypertension and Impaired Salt Excretion

BACKGROUND: In vitro studies suggest that nephron nitric oxide synthase 3 (NOS3) modulates tubule Na(+) transport. METHODS AND RESULTS: To assess nephron NOS3 relevance in vivo, knockout (KO) mice with doxycycline‐inducible nephron‐wide deletion of NOS3 were generated. During 1 week of salt loading, KO mice, as compared with controls, had higher arterial pressure and Na(+) retention, a tendency towards reduced plasma renin concentration, and unchanged glomerular filtration rate. Chronic high salt‐treated KO mice had modestly decreased total NCC and total SPAK/OSR1 versus controls, however percent phosphorylation of NCC (at T(53)) and of SPAK/OSR1 was increased. In contrast, total and phosphorylated NKCC2 (at T(96/101)) were suppressed by 50% each in KO versus control mice after chronic salt intake. In response to an acute salt load, KO mice had delayed urinary Na(+) excretion versus controls; this delay was completely abolished by furosemide, partially reduced by hydrochlorothiazide, but not affected by amiloride. After 4 hours of an acute salt load, phosphorylated and total NCC were elevated in KO versus control mice. Acute salt loading did not alter total NKCC2 or SPAK/OSR1 in KO versus control mice but increased the percent phosphorylation of NKCC2 (at T(96/101) and S(126)) and SPAK/OSR1 in KO versus control mice. CONCLUSIONS: These findings indicate that nephron NOS3 is involved in blood pressure regulation and urinary Na(+) excretion during high salt intake. Nephron NOS3 appears to regulate NKCC2 and NCC primarily during acute salt loading. These effects of NOS3 may involve SPAK/OSR1 as well as other pathways.