Angiotensin II receptor subtypes in rat renal preglomerular vessels

A simple technique to isolate rat renal preglomerular vessels is described. Kidneys were pressed against a 0.3 mm stainless steel grid. The whole vascular tree, including the interlobar, arcuate, and interlobular arteries, as well as the afferent arterioles, remained on the grid surface from where they were recovered. Extensive washing yielded a highly pure preparation of renal microvessels. Radioligand binding experiments were performed to characterize 125I-[Sar1,Ile8]-ANG II binding sites in preglomerular microvessel membranes. Equilibrium saturation binding experiments revealed the presence of one group of high affinity receptors (Kd = 1.22 +/- 0.171 nM; Bmax = 209 +/- 14 fmol/mg protein). Competitive inhibition experiments with two highly specific nonpeptide ANG II antagonists, losartan (DuP 753), which is specific for the AT1 receptor subtype, and PD123319, which is specific for the AT2 subtype, demonstrated that the large majority of, if not all, ANG II receptors in rat renal preglomerular vessels correspond to the AT1 subtype.