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

Summary: Effects of chronic treatment of dibutyryl cyclic AMP (db-cyclic AMP) on Na⁺, K⁺-ATPase activity in cell homogenates and intracellular N a f 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.