Factors influencing the growth and respiration of rat cerebral astrocytes in primary culture.

Cell densities and respiratory rates of astrocytes from neonatal rat brain grown in primary culture were determined after 20-30 days in vitro. Cells grown in flasks reached lower densities (microgram DNA/cm2) and higher protein:DNA ratios than cells grown in petri dishes. Respiratory rates were lower for cells grown in flasks compared to cells grown in dishes. The pH of the medium in flasks fell below 6.9 between feedings while the pH of the medium in dishes remained at about 7.2. Cells grown in dishes with the medium pH adjusted to 6.8 also showed lower final cell densities, higher protein:DNA ratios, and lower respiratory rates, compared to cells grown under similar conditions at pH 7.5. Intermediate values of each parameter were found in cells grown at pH 7.5 for one week and then at 6.8 for 20 days. We conclude that the effects of ambient pH account for the differences in growth characteristics and respiratory rates of astrocytes grown in dishes versus those grown in flasks.