Chronic L-NAME hypertension in rats and autoregulation of juxtamedullary preglomerular vessels.
The impact of chronic NG-nitro-L-arginine methyl ester (L-NAME)-induced hypertension (20 mg.kg-1.day-1 po, for 25 days) on pressure responsiveness was assessed in vessels ranging from arcuate arteries (ArcA) to juxtaglomerular afferent arterioles (JAA), using videomicroscopy and blood-perfused juxtamedullary nephron (JMN) preparations. Respective tail-cuff pressures of control and L-NAME rats were 127 +/- 2 (n = 8) and 173 +/- 4 mmHg (n = 5). Corresponding vessels of both groups had similar calibers at 60 mmHg. Increasing blood perfusion pressure to 200 mmHg constricted control ArcA and JAA by 26 +/- 4% (n = 20) and 43 +/- 5% (n = 15), respectively. Instead, a respective 3 +/- 4% (n = 15) and 21 +/- 9% (n = 6) pressure-induced dilation occurred in L-NAME vessels, and 86 +/- 2% of glomeruli expressed alpha-smooth muscle actin. Responses to acetylcholine (1 microM) but not to nitroprusside (1 mM) were impaired by L-NAME. Maximal relaxation induced by Mn2+ (10 mM) revealed equal basal tone and similar passive viscoelastic properties in control and L-NAME vessels. No vascular hypertrophy was found in L-NAME vessels. Chronic L-NAME hypertension is therefore associated with a selective loss of vascular autoregulation in JMNs, which may contribute to glomerular injury.
Bouriquet
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Groupe Rein et Hypertension, Hôpital St. Charles, Montpellier, France.
Casellas
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D
D000199:Actins / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives*; D001794:Blood Pressure; D001808:Blood Vessels / Q000503:physiopathology; D002908:Chronic Disease; D006439:Hemodynamics; D006706:Homeostasis; D006973:Hypertension / Q000139:chemically induced* / Q000503:physiopathology*; D007606:Juxtaglomerular Apparatus / Q000098:blood supply*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D012079:Renal Circulation
D000199:Actins; D009569:Nitric Oxide; D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester