Differential regulation of renal glomerular and preglomerular vascular angiotensin II receptors

The activity of the renin-angiotensin system (RAS) can be influenced by sodium intake and angiotensin II (ANG II) infusion. It has been shown that ANG II can regulate the density of its receptors. Therefore, we investigated the regulation of glomerular and preglomerular vascular ANG II receptors by changes in RAS activity. Sprague-Dawley rats were fed a low- or high-sodium diet or were infused with nonpressor or presser doses of ANG II for 7 days. ANG II receptor characteristics were determined by radioligand binding assays with use of ANG II antagonists losartan and PD-123319. AT(1) was the only receptor type found in membrane preparations from all groups. Glomerular ANG II receptor characteristics in all groups were unchanged compared with their controls, whereas vascular receptor density was significantly downregulated by sodium restriction. We conclude that glomerular and preglomerular vascular ANG II receptors are differentially regulated such that AT(1) receptors in preglomerular vessels can be regulated by changes in endogenous RAS. ANG II infusion did not induce any modification of either glomerular or vascular AT(1) receptors, suggesting a predominant role of the endogenous local renal RAS.