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Departamento de Fisiología, Facultad de Medicina, 30071 Murcia, Spain
Nitric oxide (NO) is a vasodilator
substance controlling renal papillary blood flow (PBF) in the rat. In
this study we have evaluated the role of
AT1 angiotensin II receptors as
modulators of the whole kidney and papillary vasoconstrictor effects
induced by the acute or chronic inhibition of NO synthesis. Experiments have been performed in anesthetized, euvolemic Munich-Wistar rats prepared for the study of renal blood flow (RBF) and PBF. In normal rats, acute administration of the NO synthesis inhibitor
N
-nitro-L-arginine methyl ester
(L-NAME) increased mean arterial pressure (MAP) and decreased RBF and PBF. Either acute or chronic treatment with the AT1 receptor
blocker losartan did not modify the decreases in RBF or PBF secondary
to L-NAME. In animals made hypertensive by chronic inhibition of NO, basal MAP was higher, whereas
RBF and PBF were lower than in the controls. In these animals, acute or
chronic administration of losartan decreased MAP and increased both RBF
and PBF significantly. These results indicate that, under normal
conditions, the decreases in RBF or PBF induced by the acute inhibition
of NO synthesis are not modulated by
AT1-receptor stimulation. However,
the arterial hypertension, renal vasoconstriction, and reduced PBF
present in chronic NO-deficient hypertensive rats is partially due to
the effects of angiotensin II, via stimulation of
AT1-receptors.
kidney; renal blood flow; N
-nitro-L-arginine methyl ester
hypertension; angiotensin II; losartan
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