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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Physiol
2016 ; 594
(21
): 6287-6300
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Exogenous and endogenous angiotensin-II decrease renal cortical oxygen tension in
conscious rats by limiting renal blood flow
#MMPMID27426098
J Physiol
2016[Nov]; 594
(21
): 6287-6300
PMID27426098
show ga
KEY POINTS: Our understanding of the mechanisms underlying the role of hypoxia in
the initiation and progression of renal disease remains rudimentary. We have
developed a method that allows wireless measurement of renal tissue oxygen
tension in unrestrained rats. This method provides stable and continuous
measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and
can reproducibly detect acute changes in cortical oxygenation. Exogenous
angiotensin-II reduced renal cortical tissue PO2 more than equi-pressor doses of
phenylephrine, probably because it reduced renal oxygen delivery more than did
phenylephrine. Activation of the endogenous renin-angiotensin system in
transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal
hypoxia precedes the development of structural pathology and can be reversed
acutely by an angiotensin-II receptor type 1 antagonist. Angiotensin-II promotes
renal hypoxia, which may in turn contribute to its pathological effects during
development of chronic kidney disease. ABSTRACT: We hypothesised that both
exogenous and endogenous angiotensin-II (AngII) can decrease the partial pressure
of oxygen (PO2) in the renal cortex of unrestrained rats, which might in turn
contribute to the progression of chronic kidney disease. Rats were instrumented
with telemeters equipped with a carbon paste electrode for continuous measurement
of renal cortical tissue PO2. The method reproducibly detected acute changes in
cortical oxygenation induced by systemic hyperoxia and hypoxia. In conscious
rats, renal cortical PO2 was dose-dependently reduced by intravenous AngII.
Reductions in PO2 were significantly greater than those induced by equi-pressor
doses of phenylephrine. In anaesthetised rats, renal oxygen consumption was not
affected, and filtration fraction was increased only in the AngII infused
animals. Oxygen delivery decreased by 50% after infusion of AngII and renal blood
flow (RBF) fell by 3.3 ml min(-1) . Equi-pressor infusion of phenylephrine did
not significantly reduce RBF or renal oxygen delivery. Activation of the
endogenous renin-angiotensin system in Cyp1a1Ren2 transgenic rats reduced
cortical tissue PO2. This could be reversed within minutes by pharmacological
angiotensin-II receptor type 1 (AT(1) R) blockade. Thus AngII is an important
modulator of renal cortical oxygenation via AT(1) receptors. AngII had a greater
influence on cortical oxygenation than did phenylephrine. This phenomenon appears
to be attributable to the profound impact of AngII on renal oxygen delivery. We
conclude that the ability of AngII to promote renal cortical hypoxia may
contribute to its influence on initiation and progression of chronic kidney
disease.