Influence of brain extract and dibutyryl cyclic AMP on the amount of carbonic anhydrase in primary glial cell cultures from newborn rat brain.

The effect of brain extracts from rat and beef, and of 2',5'-dibutyryl cyclic AMP on the CAII content was investigated in rat primary glial cultures maintained in serum-containing or serum-free medium. All cultures contained a mixed population of oligodendroglial and astroglial cells, but under certain conditions the cultures were highly enriched in oligodendroglial cells. An immunocytochemical positive reaction to CAII was observed in oligodendrocytes, while astrocytes were not stained. The content of CAII per culture and per oligodendroglial cell was higher after treatment of the culture with soluble brain extract and a partially purified fraction. A combined autoradiographic- immunohistochemical study, after [(3)H]thymidine incorporation and staining for CAII, showed that under the influence of rat brain extract the number of mitotic CAII positive cells was greater at day 11 compared to control cultures. But the proliferation rate decreased with time in culture after brain extract treatment and the number of mitotic CAII positive cells became far below that of controls. Since at the same time CAII quantity per cell was higher in the treated ones it is suggested that brain extract not only influences the proliferation of oligodendroglial cells, but also their maturation. The addition of 2' ,5'-dibutyryl cyclic AMP had no effect on oligodendroglial cells and the amount of CAII in the cultures was not affected. It is discussed that agents, which stimulate 3',5'-cyclic AMP content, may not influence the CAII content, but may stimulate the enzymatic activity.