Objective The present study was performed to examine in two-kidney, one clip (2K1C) Goldblatt hypertensive mice, first, the relative contribution of angiotensin II (ANG II) receptor subtypes 1A (AT1A) and 1B (AT1B); second, the role of ANG II type 2 (AT2) receptors in the development of hypertension in wild-type (AT1A+/+) and AT1A receptor knockout (AT1A−/−) mice and third, the role of increased nitric oxide synthase (NOS) activity in counteracting the hypertensinogenic action of ANG II in this model. Methods AT1A+/+ and AT1A−/− mice underwent clipping of one renal artery and were infused with either saline vehicle or with the selective AT2 receptor agonist CGP-42112A (CGP). Blood pressure (BP) was monitored by radiotelemetry. BP responses to the NOS inhibitor nitro-L-arginine-methyl-ester (L-NAME) were evaluated. Results AT1A+/+ mice responded to clipping by a rise in BP which was not modified by CGP infusion. Clip placement caused a slight increase in BP in AT1A−/− mice which remained significantly lower than in AT1A+/+ mice. Acute NOS inhibition caused greater increases in BP in 2K1C/AT1A+/+ than in AT1A+/+ mice. Conclusions The present data support the critical role AT1A receptors in the development of 2K1C hypertension, whereas AT1B receptors play only a minor role in BP regulation in this model of ANG II-dependent hypertension. Activation of AT2 receptors does not play an antagonistic role in the AT1 receptor-mediated hypertensinogenic actions of ANG II in this model. Finally, enhanced NOS activity plays a protective role by counteracting the vasoconstrictor influences of ANG II in 2K1C hypertensive mice.

Our results demonstrate that after induction of the renin gene in Cyp1a1-Ren-2 transgenic rats inappropriate increases in plasma and kidney ANG II levels in response to very high dietary salt intake are responsible for the development of severe hypertension in this model of inducible renin transgenic rats.

Our findings indicate that an impairment of the pressure-natriuresis mechanism precedes the development of ANG II-dependent hypertension in Cyp1a1-Ren-2 transgenic rats.

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