TIME-COURSE OF CHANGES IN LACTATE AND FREE FATTY-ACIDS AFTER EXPERIMENTAL BRAIN INJURY AND RELATIONSHIP TO MORPHOLOGIC DAMAGE

Regional levels of lactate and free fatty acids (FFA) were measured af ter lateral fluid percussion (FP) brain injury in rats. At 5 min after injury, tissue concentrations of lactate were elevated in the cortice s and hippocampi of both ipsilateral and contralateral hemispheres. Wh ereas lactate levels had returned to normal by about 20 min after inju ry in the penumbra and contralateral cortices, their elevation persist ed in the ipsilateral injured cortex and hippocampus for 24 h after in jury. Increases in the levels of FFA (particularly stearic and arachid onic acids) were observed in the cortices and hippocampi of both ipsil ateral and contralateral hemispheres at 5 min after injury; these leve ls returned to normal in only the penumbra and contralateral cortices by 20 min after injury. Increased amounts of palmitic and oleic acids were also found only in the injured left cortex and ipsilateral hippoc ampus at 20 min or later after injury. In general, these elevations pe rsisted for as long as 6 to 24 h in the injured cortex and for 2.5 to 24 h after injury in the ipsilateral hippocampus. Histologic studies r evealed a similar extent of damage in the cortex between 5 min and 24 h after injury, whereas damage in the CA3 region of the ipsilateral hi ppocampus increased during that period. These findings suggest a role for lactic acid and FFA, two secondary injury factors, in neuronal cel l loss after brain injury. (C) 1997 Academic Press.