Effects of hypoxia and recovery on brain eicosanoids and carbohydrate metabolites in rat brain cortex

Abstract

The effects of hypoxia (respiration of 5% O 2 for 30 min) and recovery (respiration of air up to 30 min) on brain levels of carbohydrate metabolites, of free arachidonate (FAA) and of several eicosanoids (E) were studied in the rat. Animals were sacrificed before or after 30 min of hypoxia, and during recovery, by microwave radiation (MW). At the end of the hypoxic period, arterial pO 2 was reduced to 28 mm Hg and glycemia was elevated. Brain lactate and glucose levels were also elevated, whereas glycogen was unchanged. Levels of free FAA and of E were practically unchanged. During recovery, arterial pO 2 values were raised above prehypoxic levels at 5 min and returned to normal within 30 min. The elevated serum glucose declined at 5 min and values returned to normal at 30. Brain glucose was still elevated at 5 min and returned to normal, together with lactate, at 30 min. Brain FAA did not change during recovery, but levels of prostaglandin F 2α (PGF 2α), prostaglandin E 2 (PGF 2) and thromboxane B 2 (TxB 2) were raised, at 5 min, and those of 6-keto-PGF 1α were reduced with respect to pre-hypoxia. At the end of recovery, all E were lower than during hypoxia. The results indicate that changes of brain E occur only during recovery from hypoxia. At 5 min of recovery, at high arterial pO 2 values, concentrations of all E were elevated, with the exception of 6-keto-PGF 1α which was reduced. At 30 min a marked reduction of E levels was observed, possibly resulting from increased clearance following elevation of cerebral blood flow.