New insights into actions of the renin-angiotensin system in the kidney: concentrating on the Ang II receptors and the newly described Ang-(1-7) and its receptor

Abstract

Angiotensin II (Ang II), the physiologically active component of the renin-angiotensin system (RAS), plays an important role in the regulation of the renal function. Based on their different pharmacologic and biochemical properties, 2 distinct subtypes of Ang II receptor have been defined and designated as type 1 (AT(1)) and type 2 (AT(2)) receptors. Most of the well-characterized actions of Ang II are now generally considered to result from stimulation of AT(1) receptors, whereas AT(2) receptors may exert opposite effects against AT(1) receptors. In the kidney, activation of the AT(2) receptor has been reported to regulate pressure-natriuresis and to stimulate the production of nitric oxide, bradykinin, or epoxyeicosatrienoic acids, which may cause vasodilation and modulate the vasoconstrictor action mediated by AT(1) receptors. In addition, recent studies have reported that Ang II exerts important effects on the normal renal development through both AT(1) and AT(2) receptors. Finally, other Ang fragments such as Ang-(1-7) are also involved in the actions of RAS in the kidney. In this review article, we will summarize results obtained from recent studies on the AT(1) and AT(2) receptor-mediated action of Ang II in the kidney. Renal actions of Ang-(1-7), which often oppose against those of Ang II, are also discussed.