Inducible ornithine decarboxylase expression in brain subject to vasogenic oedema after transient ischaemia: relationship to C-fos gene expression.

Ornithine Decarboxylase (ODC) is the rat controlling enzyme of polyamine biosynthesis and has been shown to be produced in a delayed fashion in response to cerebral ischaemia. Its appearance has been linked to the development of vasogenic brain oedema. To understand the genetic control of this protein, Mongolian gerbils were studied for the possible expression of the ODC gene as compared to that of the inducible proto oncogenes c-fos and c-jun after transient bilateral carotid artery occlusion. Total cellular RNA was isolated from gerbil brains by guanidine-thiocyanate extraction and characterized by northern blot analysis for c-fos, c-jun, and ODC mRNA over reperfusion times. c-fos and c-jun expression rose rapidly with peak level reached at 60 min of reperfusion (70 x control, p less than or equal to 0.01). Peak levels of ODC mRNA induction were seen at 4 hrs reperfusion (2.83 x control, p less than or equal to 0.01) consistent with the period of maximum of brain oedema as measured by specific gravity (1.0386 +/- 0.0009, p less than or equal to 0.05). These data indicate the differential timing of genetic expression during the reperfusion period after transient ischaemia. Such studies suggest that potential therapies may be possible by addressing the delayed ODC component of ischaemic oedema formation and allow a greater understanding of the role of gene induction in the multifaceted cerebral response to ischaemia.