Protein metabolism and electrophoretic profiles in astroglial primary cultures from different regions of newborn rat brain.

Primary astroglial cultures (14 days of age) from cerebral cortex, striatum, and hippocampus of newborn rat brain contained similar amounts of soluble proteins. Uptake and incorporation of [3H]valine into soluble protein measured after 30 and 60 min of incubation, respectively, was on a similar level in the various cultures. [3H]valine labeling of protein bands from the cell soluble fractions and incubation media of hemisphere cultures, and which were separated by isoelectric focusing (IEF) or sodium-dodecyl-sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), indicated that proteins are released to the extracellular medium after being synthesized within cultivated cells. Acidic and high molecular weight proteins were more heavily labelled in the incubation media than in the cell soluble fractions. Two-dimensional electrophoresis (IEF X SDS-PAGE) of soluble proteins from the different cultures showed similar patterns, which were quite different from the serum-free extracellular protein patterns. Both fractions were different from the pattern obtained from fetal calf-serum. In striatum and hippocampus culture media a "spot" was seen with Ip 6.0-6.8 and m.w. 105,000, and in the media from cerebellar cultures another "spot" was observed with Ip 5.2-5.6 and m.w. 55,000. The results show that the different cultures are similar in their protein synthetic capacity and protein composition. The specific differences observed in proteins obtained from the serum-free incubation media might indicate specific properties among astroglial cells from various brain regions.