Effect of hypothermia on the volume of rat glial cells

1. The cell volume of suspended CB glioma cells and primary cultured rat as trocytes was measured at normothermia (37 degrees C), and at mild (32 degre es C) and moderate (27 degrees C) hypothermia, by flow cytometry with elect rical cell sizing. 2. Under control conditions (37 degrees C), C6 glioma cells had a volume of 809 +/- 29 mu m(3). Moderate hypothermia (27 degrees C) led to rapid cell swelling, with a maximum volume of 113.1 +/- 1.3% of control being achieved after 50 min. After rewarming to 37 degrees C, cell volume recovered very slowly and incompletely (to 107.2 +/- 0.4% of control). Less severe hypothe rmia (32 degrees C) led to a smaller increase in cell volume (108.7 +/- 0.5 % of control). 3. The maximal cell swelling response and the kinetics of swelling were sim ilar in C8 glioma cells and primary cultured astrocytes. 4. Hypothermia-induced cell swelling was dependent on the presence of extra cellular Na+ and was reduced by the Na+-H+ antiporter inhibitor EIPA. 5. The underlying mechanisms of hypothermia-induced cell swelling are an in tracellular accumulation of Na+ by (1) differential effects of hypothermia on the membrane permeabilities of Na+ and K+ and (2) activation of the Na+- H+ antiporter by a shift of its activation curve to a more alkaline value.