HEMEOXYGENASE EXPRESSION AFTER REVERSIBLE ISCHEMIA OF RAT-BRAIN

Heme oxygenase (HO-1) gene expression was studied in the brains of rat s subjected to 30 min global cerebral ischemia followed by recirculati on of up to 24 h. Total RNA was isolated from the cerebral dorter, str iatum and hippocampus and reverse-transcribed into cDNA. cDNA was take n as template for PCR using HO-1-specific primers. We found that, when PCR reactions were run for 22 cycles, the amount of PCR products corr elated closely with the amount of cDNA. HO-1 gene expression was sharp ly increased after cerebral ischemia in all three brain structures stu died. In the cortex and striatum, the HO-1 mRNA content increased cons tantly after cerebral ischemia up to 24 h of recovery, being 8- and 9- fold over control after 24 h of recirculation in the cortex and striat um, respectively. In the hippocampus, HO-1 mRNA levels peaked at 4 h a fter ischemia (9-fold over control) and declined thereafter to 4.5-fol d over control 24 h after ischemia. Assuming that the observed increas e in mRNA levels is paralled by increased HO-1 protein synthesis, form ation of the products of HO reaction, biliverdin and carbon monoxide, is activated after ischemia. These products may produce different and divergent effects on the recovery from the metabolic stress produced b y cerebral ischemia.