A biochemical and immunohistological study of S100 protein in developing rat cerebellum.

Specific immune sera, one directed against S100 protein and one against glial fibrillary acidic protein (both proteins are specific astrocytic markers in rat cerebellum), were used in immunohistological methods to follow the formation and maturation of astrocytes during the postnatal development of rat cerebellum. Throughout development, S100 protein is detected only in astrocytes. Immunofluorescent Golgi epithelial cells and other astrocytes are detected in the cerebellum of newborn rat, their number increases rapidly between birth and the 10th postnatal day and then more slowly until the end of the 3rd week. In contrast, the increase in S100 protein level, measured in cerebellar homogenates by radioimmunoassay, was small until the 10th postnatal day. The greater accumulation subsequently found corresponds to an increase in the content of each astrocyte during the process of maturation.