Permanent neurologic damage remains the major factor that both causes excess mortality and limits the quality of life in patients successfully resuscitated from a cardiac arrest. A number of post-ischemic phenomena in the brain are well established sequellae to global ischemia and reperfusion, including ultrastructural damage, hypoperfusion, and inhibition of protein synthesis. Our previous work showed substantial membrane damage by radical-mediated mechanisms; however, little improvement in neurologic outcome has been observed in studies of various pharmacologic interventions directed toward inhibition of such radical-mediated damage. It is reasonable that following ischemia and reperfusion, cells will require membrane repair, even if further damage is inhibited. We hypothesize that terminal differentiation in neurons limits their capacity to repair damage to membrane lipids, consistent with some evidence of a close relation between cell replication status and the level of capability for lipid biosynthesis. Moreover, it may be possible to manipulate lipid synthesis and repair competence at the level of transcription with proteins involved in growth regulation, such as in- sulin. We will approach this hypothesis by utilizing cultured neuroblastoma B104 cells to examine their sensitivity to radical-mediated damage before and after induction of differentiation. We will then examine their capacity to reacylate fatty acids or synthesize lipids via the CDP-choline pathway before and after differentiation in both the presence and absence of radical-induced damage. In these experiments we will also utilize Northern hybridization to examine the effects of radical induced damage on induction of transcripts for an important enzyme in the CDP-choline pathway (cholinephosphate -cytidylyltransferase) and the first enzyme in the reacylation pathway (acyl-CoA synthetase). We will also examine the capacity of various insulin concentrations to effect the synthesis and reacylation of lipids and ion of transcription for the above enzymes. We will utilize a rat model of cardiac arrest and resuscitation to conduct in situ hybridization studies to regionally examine the brain for induction of these messages during reperfusion with and without supplemental insulin.
