Hyperoxia-induced protection against rat's renal ischemic damage: relation to oxygen exposure time.
BACKGROUND
Pre-exposure to hyperoxic gas (>or= 95%) has been shown to protect the heart and central nervous system from ischemia-reperfusion injury. In the present study, we investigated whether oxygen pretreatment induces delayed renal protection in rats. The possible role of some renal antioxidant agents was also investigated.


METHODS
Adult male Wistar rats were kept in a hyperoxic (HO) (>or= 95% O(2)) environment for 0.5 h, 1 h, 2 h, 3 h, 6 h, and 2 h/day for three consecutive days and 4 h/day for six consecutive days, and control group (IR) animals were kept in the cage with no HO, one day before subjecting their kidney to 40 minutes of ischemia and 24h of reperfusion. Renal function was assessed by comparing plasma creatinine (Cr), blood urea nitrogen (BUN), creatinine clearance (CLCr), and fractional excretion of sodium (FENa%). Histopathological injury score was also determined according to the Jablonski method. To examine the antioxidant system induction by hyperoxia, we measured renal catalase and superoxide dismutase activity, and renal glutathione and malondialdehyde content.


RESULTS
Our data demonstrated that only in 4 h/day HO for six consecutive days, the renal function tests (Cr, CLCr, BUN, and FENa%) and Jablonski histological injury were better than control group (p < 0.05). The beneficial effect of oxygen pretreatment in this group was associated with increased renal catalase activity compared with those obtained from control group (p < 0.05).


CONCLUSIONS
The present study demonstrates that repeated exposure to hyperoxic (>or= 95% O(2)) environment can reduce subsequent rat's renal ischemia-reperfusion damage. Induction of endogenous antioxidant system may partially explain this beneficial effect of hyperoxic preconditioning.
Trauma Research Center, Baqiyatallah University of Medical Sciences, Teheran, Iran. h.v.a73@hotmail.com
Hannaneh
H
Wahhabaghai
Bahram
B
Rasoulian
Mansour
M
Esmaili
Hossein Ali
HA
Mehrani
Hassan
H
Mohammadhosseniakbari
Mahmood
M
Mofid
Mahvash
M
Jafari
Majid
M
Noroozi
Mohsen
M
Foadoddini
Alireza
A
Asgai
Ali
A
Khoshbaten
D000704:Analysis of Variance; D000818:Animals; D002374:Catalase / Q000378:metabolism; D003404:Creatinine / Q000378:metabolism; D004195:Disease Models, Animal; D018496:Hyperoxia; D007150:Immunohistochemistry; D019194:Ischemic Preconditioning / Q000379:methods; D007668:Kidney / Q000098:blood supply; D007674:Kidney Diseases / Q000473:pathology / Q000517:prevention & control*; D007677:Kidney Function Tests; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage*; D011336:Probability; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D012039:Regional Blood Flow; D015427:Reperfusion Injury / Q000473:pathology / Q000517:prevention & control*; D013997:Time Factors
D017382:Reactive Oxygen Species; D008315:Malondialdehyde; D003404:Creatinine; D002374:Catalase; D010100:Oxygen