Influence of Hypothermia on Cell Volume and Cytotoxic Swelling of Glial Cells in Vitro
In view of the increasing significance of mild hypothermia (32 °C) as an efficient procedure of neuroprotection, the present study was performed to examine the influence of this level of hypothermia on the volume of glial cells under physiological as well
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Influence of Hypothermia on Cell Volume and Cytotoxic Swelling of Glial Cells in Vitro E. Mueller, J. Wietzorrek, F. Ringel, S. Guretzki, A. Baethmann, and N. Plesnila Institute for Surgical Research, Ludwig-Maximilians-Universitat, Munich, Germany
Summary In view of the increasing significance of mild hypothermia (32°C) as an efficient procedure of neuroprotection, the present study was performed to examine the influence of this level of hypothermia on the volume of glial cells under physiological as well as under pathological conditions. The influence of mild (32°C) and moderate (27 0c) hypothermia on cell volume and cell viability of C6 glioma cells was studied for 60 minutes in vitro. Cells were suspended in an incubation chamber under continuous control of temperature, pH and p02. Cell volume was measured by an advanced Coulter system. Hypothermia itself was causing significant cell swelling in a dose-dependent manner, which could be prevented by omission of Na+ -ions from the suspension medium, while the replacement of Cl- -ions failed to prevent cell swelling from hypothermia. Inhibition of the Na+ IH+antiporter with EIPA (5N-ethyl-n-isopropyl-amiloride, 50 11M) was significantly reducing the hypothermia induced cell swelling, indicating activation of the Na+ IH+ -antiporter. Conversely, mild or moderate hypothermia failed to prevent cell swelling from lactic acid, arachidonic acid or glutamate, i.e. agents which are mediating the development of cytotoxic brain edema in vivo in cerebral trauma, ischemia and other acute insults. The findings indicate that cerebral protection by hypothermia in vivo is most likely not attributable to an inhibition of cytotoxic brain edema. Further investigations, however, are required in vivo and in vitro to elucidate the hypothermia-induced swelling of glial cells in more detail, e.g. as to the role of the Na+ IH+ -antiporter.
Keywords: Hypothermia; cell swelling; glial cells; Na+ IH+antiporter.
the increased intracranial pressure. In recent years, hypothermia has regained interest for the treatment or prevention of secondary brain damage from acute cerebral insults [2, 3, 4]. Yet, underlying mechanisms as well as the most effective level of hypothermia affording cerebral protection while exerting minimal side effects at the cellular level are poorly understood so far. The present studies were carried out to shed more light on the influence of hypothermia on maintenance of the physiological cellular volume and its therapeutical potency on cell swelling from lactacidosis, arachidonic acid, or glutamate, respectively, which are known to mediate the development of cytotoxic brain edema in vivo. Movements of ions across cell membranes are well known to be temperature-dependent. The purpose of the current experiments was, therefore, to study the effect of hypothermia per se on the glial cell volume including activation of membrane transporters, as for example the Na+ /H+ -antiporter under these circumstances. In further experiments, the protective therapeutical potential of mild
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