Serum factors affect Na+ pump activity and DNA synthesis in cultured cerebellar neural cells

In neurone-enriched cultures derived from early postnatal rat cerebellum and maintained in serum-free medium, addition of serum (10% FCS) evoked a rapid increase in Na+ pump activity (as measured by ouabain-sensitive 86Rb accumulation) by activation of a Na+/H+ exchanger. This effect did not occur with cultured cerebellar astrocytes. In contrast, exposure to serum increased DNA synthesis ([3H]thymidine incorporation) in both cultured cerebellar astrocytes and in the neurone-enriched cultures. However, in the latter cultures this effect was shown by autoradiography to be due to contaminating astrocytes. Thus, in cultured cerebellar neural cells an enhancement of intracellular Na+ accumulation by serum factors may not be linked to initiation of DNA synthesis. Furthermore, raising intracellular Na+ by ouabain exposure actually decreased neural cellular DNA synthesis.