Hypovolemic state: involvement of nitric oxide in the aged related alterations of aquaporins-2 abundance in rat kidney.
OBJECTIVE
To examine the effect of nitric oxide (NO) on the expression and/or localization of inner medulla collecting duct aquaporin-2 water channel (AQP2) in young and adult hemorrhaged anesthetized rats.


METHODS
Rats of 2 (young) and 12 mo (adult) old (n=15) were divided into: Sham animals with and without NG-nitro-l-arginine methyl ester (L-NAME) treatment (S L-NAME and S); hemorrhaged animals (20% blood loss) with and without L-NAME (H L-NAME and H). Mean arterial pressure (MAP) was continuously monitored and AQP2 expression and inmunolocalization were evaluated at 120 min after bleeding.


RESULTS
L-NAME blunted the hypotension induced by hemorrhage at 120 min in young (106+/-2 mm Hg) and adult (103+/-4 mm Hg) rats. AQP2 expression increased after bleeding in young (from 22 to 50 densitometric units) and adult rats (from 15 to 30 densitometric units). Pretreatment with L-NAME enhanced this effect, being this rise lower in adult than young animals (young: 318%, adult: 233%). Electron microscopy showed that AQP2 labeling increased after withdrawal, being the number of gold particles smaller in adult than young animals in the inner medulla. L-NAME enhanced this effect.


CONCLUSIONS
NOS activity decreases AQP2 expression/traffick in the inner collecting duct principal cells in response to hemorrhage and this effect is lower with aging.
Arreche
Noelia
N
Department of Physiology, School of Pharmacy and Biochemistry, University of Buenos Aires, Buenos Aires, Argentina.
Fellet
Andrea
A
López
Margarita
M
López-Costa
Juan
J
Arranz
Cristina
C
Balaszczuk
Ana María
AM
D000375:Aging / Q000502:physiology*; D000818:Animals; D051399:Aquaporin 2 / Q000378:metabolism*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006470:Hemorrhage / Q000378:metabolism / Q000503:physiopathology; D020896:Hypovolemia / Q000378:metabolism*; D007150:Immunohistochemistry; D007668:Kidney / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D016253:Microscopy, Immunoelectron; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D014867:Water / Q000378:metabolism
D051399:Aquaporin 2; D004791:Enzyme Inhibitors; D014867:Water; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester