Up- and down-regulation of angiotensin II AT1-A and AT1-B receptors in afferent and efferent rat kidney arterioles.
BACKGROUND
The contractile effect of angiotensin II via AT1 receptors on the kidney arterioles is a crucial element in the kidney microcirculation. Angiotensin II also plays a role as an inhibitor via the AT1 receptors in the renin granulation of the arterioles. We have previously demonstrated that the AT1 receptors are downregulated in the renin-positive smooth muscle cells (SMCs) in contrast to renin-negative SMCs. In this study, we estimated the numbers of the AT1 receptor sub-types separately in the afferent and efferent arterioles and the renin-positive and renin-negative SMCs.


METHODS
The immunohistochemical signals of the AT1-A and AT1-B receptors were counted by stereological methods. (1)


RESULTS
The number of AT1-B receptors in the efferent arterioles (expressed in signals/microm3; mean (CV): 0.32 (0.33)) was significantly higher (78%; p<0.05) as compared with the number in the afferent arterioles (0.18 (0.11)). No differences were found in the AT1-A receptors. In a number of AT1-A receptors, significant differences (p<0.01) were detected between the afferent arteriolar renin-positive SMCs (0.13 (0.36)) and the number in renin-negative SMCs (0.25 (0.34)). The AT1-B receptors did not display any differences.


CONCLUSIONS
These results indicate that the AT1 receptor sub-types are regulated independently in the SMCs of the normal kidney arterioles.
Razga
Zsolt
Z
Department of Pathology, University of Szeged, Szeged Allomás, Hungary. razgazst@patho.szote.u-szeged.hu
Nyengaard
Jens Randel
JR
D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D001160:Arterioles / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D007668:Kidney / Q000098:blood supply* / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D012083:Renin / Q000378:metabolism; D015854:Up-Regulation
D044140:Receptor, Angiotensin, Type 1; D000804:Angiotensin II; D012083:Renin