AT2 receptor: Its role in obesity associated hypertension

The renin-angiotensin system (RAS) is a hormonal cascade that acts together to regulate blood pressure. Angiotensin II (Ang II) is the major octapeptide of RAS and mediates its cellular and physiological actions by acting on AT1 and AT2 receptor. Most of the cellular and physiological actions of Ang II such as cellular growth and proliferation, vasoconstriction, antinatriuresis and increase in blood pressure are mediated via AT1 receptor. The functions associated with the AT2 receptors are less studied, in part, due to its lower expression in adult tissues. However, AT2 receptor has been suggested as functional antagonist of AT1 receptors and thereby opposes the actions of Ang II mediated via AT1 receptor. Thus, the activation of AT2 receptors has been shown to cause vasodilatation, natriuresis and decrease in blood pressure. After the discovery of the AT2 receptor in various parts of the kidney, including in proximal tubules, there has been an interest in establishing a link between the renal AT2 receptor, renal Na-excretion and blood pressure regulation. Earlier, we have reported that activation of renal AT2 receptors increases urinary Na excretion in obese Zucker rats, in part via inhibiting Na+/K+ - ATPase (NKA) activity and stimulating nitric oxide/cGMP pathway in the proximal tubules. An impaired pressure natriuresis and increased AT1 receptor function is believed to be the cause of hypertension in obese Zucker rats and other animal models of obesity. In this review, we are focussing on the role of renin angiotensin system especially AT2 receptors in obesity associated hypertension.