Intrarenal angiotensin II and hypertension.

Elevations in intrarenal angiotensin II (Ang II) cause reductions in renal function and sodium excretion that contribute to progressive hypertension and lead to renal and vascular injury. Augmentation of intrarenal Ang II occurs by several processes, leading to levels much greater than can be explained from the circulating levels. In Ang II-dependent hypertension, Ang II is internalized via an AT1 receptor mechanism, but there is also sustained intrarenal production of Ang II. Ang II exerts a positive feedback action on intrarenal angiotensinogen (AGT) mRNA and protein. The increased intrarenal AGT production is associated with increased intrarenal and intracellular Ang II contents and urinary AGT excretion rates. The increased urinary AGT indicates spillover of AGT into distal nephron segments supporting enhanced distal Ang II formation and sodium reabsorption. The augmentation of intrarenal Ang II provides the basis for sustained actions on renal function, sodium excretion, and maintenance of hypertension.