Use of cell cultures to differentiate among effects of various ischemia factors on astrocytic cell volume.

Mouse astrocytes were subjected to in vitro models of ischemia (hypoxia with or without substrate deprivation, excess potassium, or elevated glutamate). Three hours of hypoxia alone or with substrate deprivation had little effect upon the morphology of astrocytes but did cause disaggregation of polyribosomes. Excess (12-50 mM) potassium added (as KCl) to a normal isotonic medium also caused no swelling; it did, however, cause a shrinkage of cell volume. When 50 mM potassium was substituted for a similar amount of sodium, marked swelling occurred. Swelling of astrocytes was also seen after addition of glutamate (50 microM to 1 mM) to the culture medium. These results show that ischemia per se does not result in astrocytic swelling; rather, microenvironmental alterations such as rising glutamate levels and changes in the sodium/potassium ratios result in astrocytic swelling. We conclude that one can use astrocytes in culture to dissect out the mechanisms that cause postischemic alterations in astrocytes in vivo.