A New Mechanism for the Sex Differences in Angiotensin II-Induced Hypertension---The Role of Macula Densa NOS1β-Mediated Tubuloglomerular Feedback.

Females are protected against the development of Angiotensin II (Ang II)-induced hypertension compared with males, but the mechanisms are not completely elucidated. In the present study, we hypothesized that the effect of Ang II on macula densa nitric oxide (NO) synthase β (NOS1β)-mediated tubuloglomerular feedback (TGF) mechanism is different between male and female, thereby contributing to the sexual dimorphism of Ang II-induced hypertension. We used microperfusion, micropuncture, clearance of FITC-inulin, and radio telemetry to examine the sex differences in the changes of macula densa NOS1β expression and activity, TGF response, natriuresis, and blood pressure (BP) after 2-weeks Ang II infusion in wild-type and macula densa-specific NOS1 knockout mice. In wild-type mice, Ang II induced higher expression of macula densa NOS1β, greater NO generation by the macula densa, as well as lower TGF response in vitro and in vivo in females than in males; the increases of GFR, urine flow rate and sodium excretion in response to an acute volume expansion were significantly greater and the BP responses to Ang II were significantly less in females than in males. In contrast, these sex differences in the effects of Ang II on TGF, natriuretic response and BP were largely diminished in knockout mice. Additionally, tissue culture of human kidney biopsies (renal cortex) with Ang II resulted in a greater increase in NOS1β expression in females than in males. In conclusion, macula densa NOS1β-mediated TGF is a novel and important mechanism for the sex differences in Angiotensin II-Induced hypertension.