Thyrotropin preparations are mitogenic for thyroid epithelial cells in follicles in suspension culture.

Publisher Website
Google Scholar
Abstract
The extent to which separated thyroid follicles in suspension culture, free of endothelium and fibroblasts, have the properties of follicles in vivo was investigated. To test whether thyrotropin (TSH) can cause thyroid epithelial cells to undergo mitosis, preparations of rat follicles suspended in Coon''s modified F-12 medium with 0.5% calf serum were incubated with 10 milliunits of impure or pure TSH per ml. Three results were obtained: TSH preparations stimulated the incorporation of [3H]thymidine into cell nuclei; mitotic figures were induced and they had the same characteristic ultrastructural features as those observed in vivo and the cell number doubled in the course of 3 days of exposure to TSH. TSH apparently is a mitogen for the principal thyroid epithelial cell and other substances found in the usual impure TSH preparations are not necessary for the mitogenic activity. It can act in the absence of nonfollicular cells. The initial multiplication rates are similar to those in vivo. The cells do not have to spread to divide in contrast to the requirement for spreading in the case of fibroblasts.