Effects of angiotensin II on regional afferent and efferent arteriole dimensions and the glomerular pole

The diversity of renal arteriole diameters in different cortical regions ha s important consequences for control of glomerular capillary pressure. We e xamined whether intrarenal angiotensin II (ANG II; 0.1, 1, or 5 ng . kg(-1) . min(-1))in anesthetized rabbits acts preferentially on pre- or postglome rular vessels using vascular casting. ANG II produced dose-related reductio ns in afferent and efferent diameters in the outer, mid, and inner cortex, without effecting arterial pressure. Afferent diameter decreased more than efferent in the outer and mid cortex (P< 0.05) but by a similar extent in j uxtamedullary nephrons (P = 0.58). Calculated efferent resistance increased more than afferent, especially in the outer cortex (127 vs. 24 units; 5 ng . kg(-1) . min(-1) ANG II). ANG II produced significant dose-related incre ases in the distance between the arterioles at the entrance to the glomerul ar pole in all regions. Thus afferent diameter decreased more in response t o ANG II, but efferent resistance rose more due to smaller resting luminal dimensions. The results also indicate that glomerular pole dimensions chang e in response to ANG II.