Effects of dibutyryl cyclic AMP on Na+,K(+)-ATPase activity and intracellular Na+ and K+ in primary cultures of astrocytes from DBA and C57 mice.

Abstract

Effects of chronic treatment of dibutyryl cyclic AMP (db-cyclic AMP) on Na+,K(+)-ATPase activity in cell homogenates and intracellular Na+ and K+ contents [(Na+)i and (K+)i] were studied in primary cultures of astrocytes derived from cerebral cortex of neonatal audiogenic seizure-susceptible DBA and audiogenic seizure-resistant C57 mice. Na+,K(+)-ATPase activity in cell homogenates was greater and (Na+)i was less in DBA astrocytes than in C57 astrocytes. There was no difference in (K+)i between astrocytes from DBA and C57 mice. Addition of db-cyclic AMP to the medium from day 14 to day 21 in culture (final concentration 0.25 mM) increased Na+,K(+)-ATPase activity in cell homogenates and decreased (Na+)i, but had no significant effect on (K+)i in astrocytes from either DBA or C57 mice. Chronic treatment with db-cyclic AMP altered cell growth. Protein and DNA content of cultured astrocytes from both DBA and C57 mice was decreased. DNA was more affected than protein. Modifying K+ and Na+ concentration in medium altered Na+,K(+)-ATPase activity in cell homogenates as well as (Na+)i and (K+)i in cultured astrocytes of both DBA and C57 mice. Changes in (Na+)i and (K+)i at different K+ concentrations in medium paralleled those in Na+,K(+)-ATPase activity in cell homogenates. Results indicate that the ability to transport Na+ across the cell membrane and the response of Na+,K(+)-ATPase to db-cyclic AMP and to the changes in K+ in medium of cultured astrocytes from audiogenic seizure-susceptible DBA mice are sufficient.