S100 on isolated neurons and glial cells from rat, rabbit and guinea pig during early postnatal development.

The brain specific S100 protein has been demonstrated by immunofluorescence microscopy on neuronal cell membranes during postnatal development of rat, rabbit and guinea pig. S100 has been found in glial cell aggregates of rats 4-5 days old, of rabbits 2-3 days old, and of newborn guinea pig. The neuronal plasma membrane-bound portion of the protein appears later during development. In rats 10 to 12 days of age S100 could be found on one part of the cell membrane of Deiters' neurons and of Purkinje cells. In rats 12 to 15 days old cells from the cerebral cortex contained a heterogeneously distributed cell membrane-bound portion of S100. The protein on neuronal cell membranes could be seen somewhat earlier in rabbits as compared to rats. Newborn guinea pigs showed a heterogeneous distribution of the protein similar to that seen in adult animals. In rat and rabbit adults distribution and amounts of S100 were reached at days 25-30 and at days 20-24, respectively. The results obtained here are in agreement with biochemical results. Our findings suggest that the membrane-bound part of the S100 protein with its heterogeneous and polar distribution on the nerve cell plasma membranes (demonstratable in parallel with physical and behavioral maturation of the animals) is a sign of a protein differentiation of the neuron.