Tissue-specific ceramide response in the chronically hypoxic rat model mimicking cyanotic heart disease

BACKGROUND AND OBJECTIVE: Acute hypoxia is associated with apoptosis and increase in ceramide levels in various organs. To assess the effect of chronic hypoxia on ceramide accumulation in the lungs and kidneys, we utilized an animal model mimicking cyanotic heart disease. METHODS: Rats were placed in a hypoxic environment at birth and oxygen levels were maintained at 10% in an air-tight Plexiglas chamber. Controls remained in room air. Animals were sacrificed and the lung and kidneys were harvested and weighed at 1 and 4 weeks, respectively. Ceramide levels were measured using a modified diacylglycerol kinase assay. RESULTS: Significant polycythemia developed in the hypoxic rats at 1 and 4 weeks. Indexed lung and kidney masses were significantly increased in the hypoxic animals as compared to controls at 1 and 4 weeks, respectively. The ceramide levels in the hypoxic lungs and kidneys were not significantly different from control groups at 1 and 4 weeks. Ceramide/phosphate ratio in the kidneys was 1.28 +/- 0.17 (C) versus 1.18 +/- 0.12 (H) at 1 week; P = 0.39, and 1.46 +/- 0.08 (C) versus 1.33 +/- 0.15 (H) at 4 weeks (P = 0.44)] and ceramide/phosphate ratio (pmol/nmol) in the lungs was 2.29 +/- 0.14 (C) versus 1.98 +/- 0.12 (H) at 1 week (P = 0.17), and 2.42 +/- 0.16 (C) versus 2.30 +/- 0.05 (H) at 4 weeks, P = 0.34]. CONCLUSION: The response of lungs and kidneys to chronic hypoxia includes increase in indexed mass and lack of ceramide accumulation. This is similar to the response previously reported in the chronically hypoxic brain and heart. Thus, various organs appear to have similar ceramide response pattern to chronic hypoxia.