Renin distribution in the rabbit renal microvasculature.

Immunocytochemical studies have shown that renin, which is normally located in the juxtaglomerular afferent arteriole, may also be found farther upstream toward the interlobular artery during chronic stimulation of the renin-angiotensin system. We assessed the renin distribution along the renal microvasculature using both quantitative analysis and immunocytochemistry in rabbits that received a normal sodium diet (0.48% NaCl), a low sodium diet (0.04% NaCl), or enalapril (1 mg/kg/day) for 4 weeks. From the outer cortex we microdissected 1) the proximal portion of the afferent arteriole (p-AF) extending from the interlobular artery to a point 50 microns from the glomerulus, 2) the distal 50 microns including its intact terminus (d-AF), and 3) the glomerulus without the vascular pole (GL) and measured their renin content. In controls, renin was 0.3 +/- 0.2, 27.0 +/- 5.2, and 2.8 +/- 0.5 ng angiotensin I/hr/arteriole (or GL) in the p-AF, d-AF, and GL, respectively. The low sodium diet and enalapril increased renin in the d-AF (53.1 +/- 6.9 and 68.4 +/- 8.1, respectively) but not in the GL (3.3 +/- 1.0 and 3.6 +/- 0.7). In the p-AF, both caused a small increase (delta = 1.5); however, this increase was minuscule compared with the large increase in the d-AF (delta = 41).(ABSTRACT TRUNCATED AT 250 WORDS)