(Hypertension. 1997;30:1613-1620.)
© 1997 American Heart Association, Inc.
Articles |
From the Groupe Rein et Hypertension, Institut Universitaire de Recherche Clinique, Montpellier, France.
Correspondence to Daniel Casellas, PhD, Groupe Rein et Hypertension, Institut Universitaire de Recherche Clinique, 75 rue de la Cardonille, 34093 Montpellier, Cédex 5, France. E-mail casellas{at}iurc1.iurc.montp.inserm.fr
Abstract The present study was performed to characterize structurofunctional alterations of preglomerular vessels during chronic angiotensin II (Ang II)induced hypertension (Ang II group: 400 ng · kg-1 · min-1, 10 days) and to assess the role of endothelin-1 in rats receiving Ang II and the mixed receptor antagonist bosentan (Ang II+B group: 30 mg · kg-1 · d-1, 10 days). Systolic blood pressure rose by 56±3 and 54±6 mm Hg in Ang II and Ang II+B rats, respectively. Albuminuria increased similarly in both Ang IItreated groups, reflecting glomerular barrier dysfunction. Preglomerular vessels were isolated after HCl maceration and comprised arcuate arteries and their branches, interlobular arteries (ILA), and afferent arterioles (AA). In the Ang II group, focal vascular lesions affected 36±6%, 20±5%, and 4±1% of arcuate arterial branches, ILA, and AA, respectively. They were characterized by 74% increased media thickness and accumulation of Sudan blackpositive (SB+) lipid droplets, and media cell proliferation was documented through immunohistochemistry. The occurrence of SB+ lesions was strikingly reduced with bosentan. Autoregulatory responses (AR) were assessed along ILA and AA with the use of blood-perfused juxtamedullary nephron preparations. AR were elicited by raising blood perfusion pressure from 60 to 160 mm Hg and quantified through videomicroscopy as pressure-induced constrictions. AR were inhibited in Ang IItreated rats along ILA and AA; Ang IIinduced AR changes were prevented by bosentan. Maximal relaxation induced by Mn2+ revealed equal basal tone in Ang IItreated, Ang II+Btreated, and control vessels. Chronic Ang IIinduced hypertension is therefore associated with the development of SB+ lesions and selective impairment of AR in juxtamedullary nephrons. Endothelin-1 likely mediates the structurofunctional alterations of preglomerular vasculature during Ang II hypertension.
Key Words: nephrons autoregulation basal tone glomerulopathy endothelin
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