The renin-angiotensin system (RAS) is a hormonal cascade of major critical importance to the regulation of blood pressure, fluid and electrolyte balance and kidney function. Angiotensin II (Ang II), the main effector peptide of the RAS, acts at two major receptors, AT1 and AT2. The vast majority of Ang II actions are mediated by the AT1 receptor, including cell proliferation, vasoconstriction and antinatriuresis. Much less is known concerning the functions of the AT2 receptor. Recent studies indicate that the AT2 receptor inhibits cell growth and induces vasodilation opposing the effects of Ang II at AT1 receptors. The role of the AT2 receptors in fluid and electrolyte homeostatsis is unknown. The Principal Investigator has preliminary data demonstrating that the AT2 receptor mediates natriuresis in normal Sprague-Dawley rats and that the heptapeptide derivative of Ang II, des-aspartyl-Ang II (Ang III), is the preferred agonist. The Principal Investigator also has preliminary data strongly suggesting that dopamine D1-receptor stimulation induces increased renal proximal tubule cell apical membrane AT2 receptor expression and that inhibition of AT2 receptors abolishes D1 receptor-induced natriuresis. This project will explore in depth the site and mechanisms of AT2 receptor-induced natriuresis. The project will focus on two specific hypotheses: (1) AT2 receptors in the renal proximal tubule are key mediators of the natriuretic responses to Ang III, AT1 receptor blockade, D1 receptor activation and increased renal perfusion pressure;and (2) AT2 receptor-mediated natriuresis is defective in young pre-hypertensive spontaneously hypertensive rats (SHR). The project will apply a combination of state-of-the-art in vivo and cell and molecular techniques to clarify the role of the AT2 receptor in sodium excretion in hypertension. These studies will help clarify the pathophysiology of human primary hypertension, a disorder affecting one-quarter after adult population in the Western world.

Public Health Relevance

Hypertension (high blood pressure), present in over 25% of the population of the Western world, is a major risk factor for heart and blood vessel disease leading to premature death and disability. Retention of salt and water by the kidney is required for hypertension to develop. This application will increase our understanding of the mechanisms whereby the kidney renin-angiotensin system regulates salt and water excretion, suggesting new molecular targets for the treatment and prevention of hypertension.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Hypertension and Microcirculation Study Section (HM)
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OH, Youngsuk
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University of Virginia
Internal Medicine/Medicine
Schools of Medicine
United States
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Kemp, Brandon A; Howell, Nancy L; Gildea, John J et al. (2014) AT? receptor activation induces natriuresis and lowers blood pressure. Circ Res 115:388-99
Kemp, Brand A; Howell, Nancy L; Gildea, John J et al. (2014) Response to letter regarding article, ""AT2 receptor activation induces natriuresis and lowers blood pressure"". Circ Res 115:e26-7
Padia, Shetal H; Carey, Robert M (2013) AT2 receptors: beneficial counter-regulatory role in cardiovascular and renal function. Pflugers Arch 465:99-110
Carey, Robert M (2013) The intrarenal renin-angiotensin and dopaminergic systems: control of renal sodium excretion and blood pressure. Hypertension 61:673-80
Carey, Robert M; Padia, Shetal H (2013) Role of angiotensin AT(2) receptors in natriuresis: Intrarenal mechanisms and therapeutic potential. Clin Exp Pharmacol Physiol 40:527-34
Carey, Robert M (2012) Functional intracellular renin-angiotensin systems: potential for pathophysiology of disease. Am J Physiol Regul Integr Comp Physiol 302:R479-81
Kemp, Brandon A; Bell, John F; Rottkamp, Daniele M et al. (2012) Intrarenal angiotensin III is the predominant agonist for proximal tubule angiotensin type 2 receptors. Hypertension 60:387-95
Gildea, John J; Wang, Xiaoli; Shah, Neema et al. (2012) Dopamine and angiotensin type 2 receptors cooperatively inhibit sodium transport in human renal proximal tubule cells. Hypertension 60:396-403
Carey, Robert M; Schoeffel, Cynthia D; Gildea, John J et al. (2012) Salt sensitivity of blood pressure is associated with polymorphisms in the sodium-bicarbonate cotransporter. Hypertension 60:1359-66
Padia, Shetal H; Kemp, Brandon A; Howell, Nancy L et al. (2012) Mechanisms of dopamine D(1) and angiotensin type 2 receptor interaction in natriuresis. Hypertension 59:437-45

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