Biochemical characteristics of C-6 glial cells.

C-6 glial cells were studied in culture with respect to morphological and biochemical changes under several experimental conditions. Doubling time was 33 hr for cells plated at either 0.5 or 1.0×10(6) cells per flask. Markedly reduced cell growth and astrocyte-like appearance were observed following dibutyryl cyclic AMP (DBcAMP) treatment. An inverse relationship between cell density and DNA, RNA, and protein content per cell was observed. AChE and BuChE activities were also inversely related to cell density, and treatment with DBcAMP increased enzyme activity, but did not alter the cell density relationship. Uptake of(3)H-norepinephrine also decreased with increasing cell density. In DBcAMP-treated cells,(3)H-NE uptake was markedly lower than in nontreated controls, and cortisol treatment decreased the uptake of(3)H-NE in DBcAMP-treated cells further still. We interpreted the foregoing changes to indicate that cellular activity is cell density-dependent.