Aim: 

In all organisms, changes in O₂ concentration represent a fundamental physiological stimulus resulting in acute and chronic responses. Certainly hypoxia causes mitochondrial dysfunctions which are involved in apoptosis and necrosis. The aim of this study was to evaluate the role of oxygen-glucose deprivation on the physiological behaviour of rat cortical astrocytes.

Methods: 

Rat cortical astrocytes were prepared from brains of newborn Sprague-Dawley rats. Cells were distributed at a concentration of 8 x 10⁴ cells/ml in DMEM without glucose in 96 well plates and placed in a humidified incubator at 37 °C in 95% N₂: 5% CO₂ atmosphere for 12 h. Control cells were placed in a different incubator with 95% air : 5% CO₂ atmosphere. At the end of anoxia period cells were incubated in normoxia for 24 h. Immediately after anoxia and the reoxygenation period we evaluated cell viability, nitric oxide (NO) production, intracellular calcium concentration [Ca²⁺]_i, the mitochondrial membrane potential and lactate production.

Results: 

After anoxia and glucose deprivation the number of cells was unmodified, but cell viability was significantly reduced in respect to control samples. NO increased significantly after anoxia and cells were significantly depolarized. Finally the [Ca²⁺]_i significantly decreased and lactate remained practically unvaried. After reoxygenation values returned similar to controls.

Conclusion: 

It is well known that after anoxia Ca²⁺ transients increased and the ion is accumulated into the mitochondria; accordingly we observed a significant decrease of the [Ca²⁺]_i. The increase of Ca²⁺ into the mitochondria activates mitochondrial NOS which increases NO release, production of ROS and membrane depolarization.