Angiotensin II and renal medullary blood flow in Lyon rats

The present study evaluated the acute effects of ANG II (5-480 ng/kg iv) and phenylephrine (PE; 0.2-146 µg/kg iv) on total renal (RBF) and medullary blood flow (MBF) in anesthetized Lyon hypertensive (LH) and low-blood-pressure (LL) rats. ANG II and PE induced dose-dependent decreases in both RBF an...

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Bibliographic Details
Published in:American journal of physiology. Renal physiology 2003-02, Vol.53 (2), p.F365-F372
Main Authors: SARKIS, Albert, KIAO LING LIU, MING LO, BENZONI, Daniel
Format: Article
Language:English
Subjects:
Arterial hypertension. Arterial hypotension
Biological and medical sciences
Blood
Blood and lymphatic vessels
Cardiology. Vascular system
Experimental diseases
Kidneys
Medical sciences
Rodents
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Summary:The present study evaluated the acute effects of ANG II (5-480 ng/kg iv) and phenylephrine (PE; 0.2-146 µg/kg iv) on total renal (RBF) and medullary blood flow (MBF) in anesthetized Lyon hypertensive (LH) and low-blood-pressure (LL) rats. ANG II and PE induced dose-dependent decreases in both RBF and MBF, which were greater in LH than in LL rats. Interestingly, after ANG II, but not after PE, the initial medullary vasoconstriction was followed by a long-lasting and dose-dependent vasodilation that was significantly blunted in LH compared with LL rats. The mechanisms of the MBF effects of ANG II were studied in LL rats only. Blockade of AT1 receptors with losartan (10 mg/kg) abolished all the effects of ANG II, whereas AT2 receptor blockade with PD-123319 (50 µg kg1 min1 iv) did not change these effects. Indomethacin (5 mg/kg) decreased by ~90% the medullary vasodilation induced by the lowest doses of ANG II (from 15 ng/kg). In contrast, NG-nitro-L-arginine methyl ester (10 mg/kg and 0.1 mg kg1 min1 iv) and the bradykinin B2-receptor antagonist HOE-140 (20 µg/kg and 10 µg kg1 min1 iv) markedly lowered the medullary vasodilation at the highest doses of ANG II only. In conclusion, this study shows that LH rats exhibit an altered MBF response to ANG II compared with LL rats and indicates that the AT1 receptor-mediated medullary vasodilator response to low doses of ANG II is mainly due to the release of PGs, whereas the dilator response to high doses of ANG II has additional nitric oxide- and kinin-dependent components.
ISSN:1931-857X
1522-1466