Redistribution of glucose-6-phosphate dehydrogenase in response to cerebral ischemia in rat brain

Glucose-6-phosphate dehydrogenase (G6PD), a cytoplasmic enzyme, plays a protective role during oxidative stress in eucaryotic cells, since they provide coenzymes and substrates to the primary antioxidant enzymes. The redistribution of G6PD in the hippocampus was studied post-ischemia (PI). There was a characteristic localisation of G6PD in pyramidal cell layers of the rat hippocampus. In hippocampus CA1 cells were stained weakly whereas CA3 cells showed strong histochemical staining. Ischemia induced up-regulation of G6PD in the hippocampus was in a specific manner. First, the activity increased in the whole hippocampus (at 4 hours PI) which persisted 6 hrs PI in CA1 area. However G6PD activity decreased in the CA3 area & dentate gyrus. At 10 & 24 hrs PI, activity decreased in CA1 area but normalised in CA3 area & dentate gyrus compared to controls. This suggests that the sensitive CA1 neurons are transiently capable of generating an anti-oxidative arsenal to cope with the oxidative stress in the first few hours PI. We can conclude that the brain contains inducible endogenous mechanisms that are capable of enhancing the ability of neurons to withstand lethal ischemic challenge. (Presently working in Vardhman Mahavir Medical College & Safdarjung Hospital, New Delhi)