Distribution of angiotensin AT1 and AT2 receptor subtypes in the rat kidney

ANG II contributes importantly to the regulation of renal vascular resistance, glomerular filtration, and tubular epithelial transport, yet there remains a paucity of information regarding the localization of the ANG II type 1 and 2 (AT(1) and AT(2)) receptors within the rat kidney particularly within the vasculature. The present study was designed to localize the transcriptional and translational site(s) of AT(1) and AT(2) receptor (AT(1)R and AT(2)R, respectively) expression within the rat kidney. Using immunohistochemistry, we detected the AT(1)R translational sites throughout the kidney, with the strongest labeling found in the vasculature of the renal cor tex and the proximal tubules of the outer medulla. The AT(2)R protein expression was found throughout the rat kidney, although there was little to no expression found in the glomerulus and medullary thick ascending limbs of Henle (TAL). Gene-specific primers were then designed to distinguish between the receptor subtypes within microdissected renal tubular and vascular segments using RT-PCR. AT(1A)R, AT(1B)R, and AT(2)R mRNA were found within the renal vasculature (afferent arterioles, arcuate artery, and outer medullary descending vasa recta). The mRNA for bath the AT(1)R isoforms was also detected in the glomeruli and the renal tubules (proximal tubules, TAL, and collecting ducts); however, no AT(2)R mRNA was detected within the glomerulus and was inconsistently found within the medullary TAL (MTAL). Taken together, these data show that mRNA for the AT(1)R subtypes was located in all of the renal tubular and vascular segments. Evidence for AT(2)R mRNA was also found in all but two of the vascular and tubular segments, the MTAL, and the glomeruli. These results are consistent with the whole tissue immunohistochemically localized receptors.