DEFENSE-MECHANISMS PROTECTING GLIAL-CELL CULTURES AGAINST THE TOXICITY OF LEAD

Several defence mechanisms against the toxicity of triethyllead (TEL) in cultures of glial cells have been studied. In contrast to cultures of glioma C-6 cells, primary cultures of glial cells generated a resis tance to the toxicity of TEL, which increased with the age of the cult ures. When the time of exposure of glial cells was extended from 24 ho urs to 6 days and the cells were exposed to increasing doses of TEL, t he activities of several metabolic enzymes were stimulated by concentr ations of TEL over 10-(7)M. Among these were glucose-6-phosphate-dehyd rogenase and acid phosphatase. On the other hand, lactate dehydrogenas e activity was not significantly affected under these experimental con ditions. When the cultures were exposed to 10(-8)M. TEL, the cellular calcium content increased and the potassium content fell. This indicat es that the activation of metabolic enzymes is a response to early eve nts in the toxic process, which include disturbances in calcium metabo lism. When glial cells were incubated with lead and selenium simultane ously, the uptake of lead into the cells was reduced, and the cellular calcium content was increased by selenium.