Primary cultures from defined brain areas. III. Effects of seeding time on [3H]L-glutamate transport and glutamine synthetase activity

Abstract

Primary astroglial-enriched cultures from various brain regions were studied with respect to age at seeding and time in culture and its effect on the [3H]L-glutamate transport capacity and glutamine synthetase (G.S.) activity. Three phylogenetically different rat brain areas were used: cerebral cortex, striatum and brainstem. There was a high-affinity and high-capacity [3H]glutamate uptake during development in all cultures studied with Km in the microM range and Vmax in the nmol range. Vmax was most prominent in cultures seeded from newborn rat cerebral cortex and striatum when grown for 2 weeks and in brainstem cultures seeded from 17-day-old rat embryos when grown for 4 weeks. There were no significant differences in Vmax comparing the cultures from the various brain regions, that is when seeded from 17-day-old embryos and grown for 2 or 3 weeks in culture. The G.S. activity was determined under similar culture conditions as above. The highest enzyme activities were found in cultures from cerebral cortex and striatum seeded from newborn and 7-day-old rats and grown for 2 or 3 weeks. G.S. activity increased during postnatal maturation in cerebral cortex, striatum and brainstem, the highest activity values being found in cerebral cortex and striatum. Vmax for glutamate uptake and G.S. activity showed many similarities in the respective cultures during cultivation. Both parameters were affected by age at seeding and time in culture. The differences between the cultures from the various brain regions, with lower values in cultures from brainstem, indicated a heterogeneity among astroglial cells in the brain regions studied.