Submitted on June 30, 2005
Accepted on December 1, 2005
Efferent arterioles exclusively express the subtype 1A angiotensin receptor: Functional insights from genetic mouse models
Lisa M. Harrison-Bernard1*, Christopher J. Monjure2, and Benjamin J. Bivona2
1 Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, LA, USA; Department of Physiology, Tulane University Health Sciences Center, New Orleans, LA, USA
2 Department of Physiology, Louisiana State University Health Sciences Center, New Orleans, LA, USA
* To whom correspondence should be addressed. E-mail: lharris{at}lsuhsc.edu.
Angiotensin (Ang) type 1A receptor null (AT1A-/-) mice exhibit reduced afferent arteriolar (AA) constrictor responses to AngII compared to wild-type (WT) mice, while efferent arteriolar (EA) responses are absent (Am. J. Physiol. Renal Physiol. 284:538-545, 2003). In the present study, the renal arteriolar constrictor responses to norepinephrine (NE) and/or AngII were determined in blood perfused juxtamedullary nephrons from kidneys of AT1A-/-, AT1B-/-, and WT mice. Baseline AA diameters were not different (13.1±0.9 vs 12.6±0.9 µm; n=7, 8); however, EA diameters were significantly larger (17.3±1.4 vs 11.7±0.4 µm; n=10, 8) in AT1A-/-compared to WT mice, respectively. NE (0.1-1 µM) produced similar constriction of AA (-40±8 vs -51±6%; 1µM) and EA (-29±6 vs -38±3%; 1 µM) of AT1A-/- and WT mice. Baseline AA (13.5±0.7 vs 14.2±0.9 µm; n=9, 10) and EA (15.4±1.0 vs 15.0±0.7 µm; n=11, 9) diameters, and AngII (0.1-10nM) constrictor responses of AA (-25±4 vs -31±5%; 10nM) and EA (-32±6 vs -35±7%; 10nM) were similar in AT1B-/- and WT mice, respectively. AngII constrictions were eliminated by AT1 receptor blockade (4 µM Candesartan). Taken together, our data demonstrate that AA and EA responses to NE are unaltered in the absence of AT1A receptors, and AngII responses remain intact in the absence of AT1B receptors. Therefore, we conclude that both AT1A and AT1B receptors are functionally expressed on the AA, while the EA exclusively expresses the AT1A receptor subtype.
