Effects of thyroid state and undernutrition on S100 protein and astroglia development in rat cerebellum.

The developmental pattern of S100 protein, a specific marker of astroglia, was studied by radioimmunoassay in the cerebellum of thyroid-deficient, thyroxine-treated and undernourished rats during development. In the control animals, the S100 protein content of the cerebellum increased maximally after the 3rd postnatal week, i.e., after cell multiplication had stopped and when the cerebellum had acquired more than 70% of its adult weight and protein content. This developmental pattern of S100 protein reflected essentially the maturation of astroglia. In the thyroxine-treated rats the total amount and the concentration of S100 protein were higher than in controls during the first 3 weeks of postnatal life and returned to normal values thereafter. In the thyroid-deficient rats both the amount and concentration were lower than in controls throughout development. In the undernourished animals the amount of S100 protein per organ was also lower than in controls during the whole experimental period studied; the S100 protein concentration was higher during the first 2 postnatal weeks and became lower thereafter. These results are discussed taking into consideration previous histological and ultrastructural observations on the effects of altered thyroid state and undernutrition on the formation and maturation of cerebellar astrocytes.