BEHAVIOR OF NITRIC-OXIDE SYNTHASE IN RAT CEREBELLAR GRANULE CELLS DIFFERENTIATING IN CULTURE

The possible relation between nitric oxide synthase (NOS) activity and neural differentiation was investigated using primary cultures of rat cerebellar granule cells differentiating in culture, NOS activity was measured in the cytosolic and particulate fractions obtained from cel l homogenate, In the experimental conditions used the optimal pH for N OS activity was about 6.4, the activity being about 3-fold higher than at pH 7.4, Cerebellar granule cell differentiation was associated wit h marked increases in NOS activity, In undifferentiated cells the enzy me was almost evenly distributed between the cytosolic and particulate fractions, during differentiation there was a 12-fold increase in act ivity in the cytosolic enzyme and a 3-fold increase in the particulate one. This indicates a marked preferential enrichment of the cytosolic enzyme during differentiation. Cerebellar granule cells produced and released NO in the culture medium; NO formation being markedly higher in differentiated cells (7-12 DIC) than in undifferentiated (2-3 DIC) ones, These data demonstrate a relationship between NOS expression and NO production and the differentiation of cerebellar granule cells, su pporting the notion that NO may play a role in this process. (C) 1997 Federation of European Biochemical Societies.