Up-regulation of gamma-glutamyl transpeptidase (GGT) activity in growth perturbed C6 astrocytes.
Activity of gamma-glutamyl transpeptidase (GGT) was studied in astrocyte-like C6 glial cells modulated in growth and maturation by different concentration of serum and dibutyryl cyclic AMP (Db-cAMP) supplement in culture medium. After reduction of serum concentration from 10% to 0.1%, the number of GGT positive cells determined histochemically increased 3.1 times and the GGT activity/mg protein in whole cell lysates was 5.1 times higher. In cultures with 0.1% serum + Db-cAMP, the histochemically and biochemically assayed GGT activity exceeded 5.1 and 7.9 times the values measured in control 10% serum cultures, respectively. The up-regulation of GGT was accompanied by an inhibition of proliferation, enhanced differentiation and hypertrophy of cells. In addition, the process of metabolic perturbation and/or cellular stress was revealed in these cultures by the (i) growth-support release followed by shrinkage and death of a small number of cells and (ii) higher oxidation of 2'7'dichlorofluorescein diacetate to its fluorescent form in the adherent/viable cells. The observed up-regulation of GGT is considered to primarily reflect increased metabolism of glutathione and/or the maintenance of the redox potential in cells stressed by sub-optimal concentration of serum and Db-cAMP supplement. The concomitant cellular hypertrophy and differentiation and their relationship to increased activity of GGT await further investigation. The study suggests that up-regulation of GGT can contribute to adaptation of astrocytic cells to metabolic and/or oxidative perturbances occurring under various pathological conditions, including radiation- and drug-induced toxicity.
Mares
V
V
Joint Laboratory of Cancer Cell Biology of the First Faculty of Medicine, Charles University and Institute of Physiology, Academy of Sciences, Videńská 1083, CZ-14200 Prague, Czech Republic. maresv@biomed.cas.cz
Malík
R
R
Lisá
V
V
Sedo
A
A
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000201:enzymology*; D003994:Bucladesine / Q000494:pharmacology; D002452:Cell Count / Q000379:methods; D016923:Cell Death; D049108:Cell Enlargement / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005452:Fluoresceins / Q000494:pharmacology; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006651:Histocytochemistry / Q000379:methods; D051379:Mice; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D017077:Culture Media, Conditioned; D005452:Fluoresceins; D005904:Glial Fibrillary Acidic Protein; C029569:diacetyldichlorofluorescein; D003994:Bucladesine; D005723:gamma-Glutamyltransferase