Estimation of the number of angiotensin II AT1 receptors in rat kidney afferent and efferent arterioles.
OBJECTIVE
To examine the effects of the renin-angiotensin system (RAS) on renal arterioles to determine the association between the distribution of angiotensin II AT1 receptors and the morphologic and physiologic heterogeneity of renal arterioles.


METHODS
To estimate the number of angiotensin II AT1 receptors along the length of the arterioles and per arteriole, we combined immunoelectron microscopy with stereology.


RESULTS
The number of AT1 receptor molecules was significantly lower in the renin-positive smooth muscle cells (SMCs) than in the renin-negative SMCs of the afferent and efferent arterioles. There were no significant differences along and between the afferent and efferent arterioles in relative number of AT1 receptors of endothelial cells or SMCs.


CONCLUSIONS
Our results suggest that the heterogeneous activity of angiotensin II in SMCs and the different permeabilities of the endothelium along the afferent arterioles are probably not controlled directly by angiotensin II AT1 receptors. However, the activity of the RAS is possibly involved in the significantly reduced number of receptors in renin-granulated cells. An understanding of how the number of AT1 receptors on the SMC surface is controlled may furnish a new path for pharmacologically changing RAS activity on SMCs.
Razga
Zsolt
Z
Stereology and Electron Microscopy Research Laboratory and MIND Center, University of Aarhus, Aarhus, Denmark. razgazst@patho.szote.u-szeged.hu
Nyengaard
Jens Randel
JR
D000344:Afferent Pathways / Q000378:metabolism; D000818:Animals; D001160:Arterioles / Q000378:metabolism / Q000648:ultrastructure; D004525:Efferent Pathways / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D017979:Gold Colloid; D007606:Juxtaglomerular Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D007678:Kidney Glomerulus / Q000098:blood supply* / Q000648:ultrastructure; D008297:Male; D016253:Microscopy, Immunoelectron; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism* / Q000648:ultrastructure; D012084:Renin-Angiotensin System / Q000502:physiology*; D013194:Staining and Labeling
D017979:Gold Colloid; D044140:Receptor, Angiotensin, Type 1