Original ContributionsProduction of hydroxyl free radical by brain tissues in hyperglycemic rats subjected to transient forebrain ischemia
Introduction
Transient cerebral ischemia is known to give rise to postischemic production of ROS. Such production was first demonstrated by Cao et al. [1], who assessed the hydroxylation of intraperitoneally administered SA in gerbils subjected to 2, 5, or 15 min of forebrain ischemia. The results (see also [2]) demonstrated that enhanced hydroxylation of the salicylate molecule, yielding the 2,3- and 2,5-metabolites, was observed after 5 and 15 (but not 2) min of ischemia, the rate of hydroxylation being larger in the hippocampus than in the neocortex. These results were confirmed in rats in which microdialysis techniques were used to assess ROS production by spin trapping [3], [4].
Additional aspects on this subject have been published. Thus the time course of changes in ROS production has been studied by Dirnagl et al. [5], who recorded continuously the chemiluminescence associated with ROS production before, during, and after transient ischemia. Further, the microdialysis techniques of Piantadosi and Zhang [6] allowed them to assess a mitochondrial origin of the ROS produced.
It is widely assumed that ROS formed during reperfusion after transient ischemia contribute to the reperfusion damage incurred [7], [8], [9]. Indirect evidence supporting this notion was reported by Kil et al. [10], who noted that hyperthermia (39°C) enhanced and hypothermia (30°C) attenuated the postischemic production of 2,3-DHBA.
In the present study, we used the salicylate technique reported by Cao et al. [1] to explore whether preischemic hyperglycemia, which is known to aggravate ischemic damage in animals subjected to transient ischemia (for reviews, see [11], [12]), leads to an exaggerated production of ROS during recirculation. To that end, rats were injected intraperitoneally with SA (100 mg/kg) and subjected to 15 min of forebrain ischemia, tissues being sampled after 5, 15, and 60 min of recirculation for analyses of salicylic acid as well as of 2,3- and 2,5-DHBA.
Section snippets
Operative procedures
Male Wistar rats of an SPF strain (Møllegaard’s Breeding Center, Copenhagen, Denmark), weighing 290–340 g, were used. The animals were not fed the night before the day of the operation, with free access to water. Anesthesia was induced by inhalation of 3.5% halothane in a mixture of N2O and O2 (70:30). After intubation with a polyethylene tubing (Intramedic PE 240, Clay-Adams, New York, NY, USA), the animals were connected to a mechanical ventilator. Anesthesia was maintained with 1.0%
Results
The plasma glucose concentrations and physiologic variables were measured 10 min before ischemia. Plasma glucose was approximately 20 mM in hyperglycemic animals and approximately 6 mM in normoglycemic ones. The level of PCO2 was kept close to 35 mmHg, PO2 was kept to above 100 mmHg, and pH was kept to 7.40. Both head and body temperatures were controlled close to 37°C, and mean arterial blood pressure was kept to 120 mmHg. There were no statistically significant differences in physiologic
Discussion
A pathogenic role for free radical-induced lipid peroxidative processes in cerebral ischemic damage was first proposed by Demopoulos et al. [18]. Since then, many studies have been carried out that demonstrate the importance of the free radical-induced damage (for data and reviews see [18], [19], [20], [21], [22], [23], [24]. Such experiments give strong support to the contention that free radicals play an important role in ischemia–reperfusion brain damage. Furthermore, free radical scavengers
Acknowledgements
This study was supported by the U.S. Public Health Service via the National Institute of Health (Grant 5 R01NS07838), the Juvenile Diabetes Foundation International, and the Queen Emma Foundation in Hawaii.
References (60)
- et al.
Oxygen free radical involvement in ischemia and reperfusion injury to brain
Neurosci. Lett.
(1988) - et al.
Evidence for formation of hydroxyl radicals during reperfusion after global cerebral ischemia in rats using salicylate trapping and microdialysis
Neorobiol. Dis.
(1994) - et al.
Detection of free radicals during brain ischemia and reperfusion by spin trapping and microdialysis
Neurosci. Lett.
(1992) - et al.
Sensitive assay of hydroxyl free radical formation utilizing high liquid chromatography with electrochemical detection of phenol and salicylate hydroxylation products
J. Free Radic. Biol. Med.
(1984) - et al.
Use of salicylate with high pressure liquid chromatography and electrochemical detection (LCED) as a sensitive measure of hydroxyl free radicals in adriamycin treated rats
J. Free Radic. Biol. Med.
(1986) - et al.
Central nervous system trauma and stroke. II. Biochemical considerations for oxygen radical formation and lipid peroxidation
Free Radic. Biol. Med.
(1989) - et al.
Central nervous system trauma and stroke. I. Physiological and pharmacological evidence for involvement of oxygen radicals and lipid peroxidation
Free Radic. Biol. Med.
(1989) - et al.
Effect of acidosis and anoxia on iron delocalization from brain homogenates
Biochem. Pharmacol.
(1992) - et al.
Effects of dimethylthiourea treatment on ischemic brain damage in hyperglycemic rats
J. Neurol. Sci.
(1992) - et al.
Ischemia-induced brain iron delocalizationeffect of iron chelators
Free Radic. Biol. Med.
(1994)