Lack of apoptosis in the hypoxic brain of a rat model mimicking cyanotic heart disease.

OBJECTIVE: To assess the effect of chronic hypoxia on brain neuronal apoptosis, an animal model mimicking cyanotic heart disease was utilized. METHODS: Rats were placed in an hypoxic environment at birth and oxygen levels were maintained at 10% in an air-tight Plexiglass chamber. Controls remained in room air. Animals were sacrificed and the brains were harvested at 1 and 4 weeks, respectively. RESULTS: Significant polycythemia developed in the hypoxic rats at 1 and 4 weeks. Indexed brain mass to body weight was significantly increased in the hypoxic groups by 18% (p < 0.01) and 38% (p < 0.01) as compared to controls at 1 and 4 weeks, respectively. There was no difference in the number of apoptotic neurons between the chronically hypoxic rats and controls, as assayed by TUNEL labelling and Hoechst staining. The role of the sphingolipid ceramide was then examined because of its reported role in stress response, growth suppression and apoptosis. It was found that the brain ceramide accumulation was not significantly different in the hypoxic and control groups at 1 and 4 weeks. CONCLUSION: A protective adaptive response to chronic hypoxia in the neonatal brain may exist.