title: Extracellular ascorbic acid fluctuation during the protective process of ischemic preconditioning in rabbit renal ischemia-reperfusion model measured.
abstract: BACKGROUND
  Ascorbic acid has important antioxidant properties, and may play a role in the protective effects of ischemic preconditioning on later ischemia-reperfusion. Herein, we examined the role of endogenous extracellular ascorbic acid in ischemic preconditioning in the kidney.
  
  
  METHODS
  We developed a solitary rabbit kidney model where animals received ischemia-reperfusion only (ischemia-reperfusion group, n = 15) or ischemic preconditioning followed by ischemia-reperfusion (ischemic preconditioning group, n = 15). Ischemia-reperfusion was induced by occluding and loosening of the renal pedicle. The process of ischemic preconditioning included 15-minute brief ischemia and 10-minute reperfusion. In vivo microdialysis coupled with online electrochemical detection was used to determine levels of endogenous extracellular ascorbic acid in both groups. The extent of tissue damage was determined in kidney sections stained with hematoxylin and eosin. Serum creatinine and urea nitrogen were also detected to assess renal function.
  
  
  RESULTS
  During ischemia-reperfusion, the extracellular ascorbic acid concentration during ischemia increased rapidly to the peak level ((130.01 +/- 9.98)%), and then decreased slowly to near basal levels. Similar changes were observed during reperfusion (peak level, (126.78 +/- 18.24)%). In the ischemic preconditioning group there was a similar pattern of extracellular ascorbic acid concentration during ischemic preconditioning. However, the ascorbic acid level was significantly lower during the ischemia and early reperfusion stage compared to the ischemia-reperfusion group. Additionally, the extent of glomerular ischemic collapse, tubular dilation, tubular denudation, and loss of brush border were markedly attenuated in the ischemic preconditioning group. Levels of serum creatinine and urea nitrogen were also decreased significantly in the ischemic preconditioning group.
  
  
  CONCLUSIONS
  Ischemic preconditioning may protect renal tissue against ischemia-reperfusion injury via use of extracellular ascorbic acid. In vivo microdialysis coupled with online electrochemical detection is effective for continuous monitoring extracellular ascorbic acid in the renal cortex.
authors.affiliation: Department of Urology, Peking University Third Hospital, Beijing 100191, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Yu-qing
authors.initials: YQ
authors.lastname: Lin
authors.forename: Long-tao
authors.initials: LT
authors.lastname: Yan
authors.forename: Kai
authors.initials: K
authors.lastname: Hong
authors.forename: Xiao-fei
authors.initials: XF
authors.lastname: Hou
authors.forename: Lan-qun
authors.initials: LQ
authors.lastname: Mao
authors.forename: Lu-lin
authors.initials: LL
authors.lastname: Ma
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D004195:Disease Models, Animal; D019194:Ischemic Preconditioning / Q000379:methods*; D007668:Kidney / Q000378:metabolism* / Q000473:pathology; D011817:Rabbits; D015427:Reperfusion Injury / Q000517:prevention & control*
chemical_list: D001205:Ascorbic Acid