Thyroid hormone action: induction of morphological changes and stimulation of cell growth in rat pituitary tumor GH3 cells.

The effects of thyroid hormones on morphology and growth were studied in rat pituitary tumor GH3 cells using medium containing serum depleted of thyroid hormones. T3 and T4 induce the cells to change from a flattened fibroblastic morphology to a rounded or spindle-shaped morphology. The induction in morphological changes is T3 and T4 specific and dose dependent. Thyronine and rT3 are ineffective in inducing morphological changes; the half-maximal effective concentrations for T3 and T4 are 0.3 and 2 nM, respectively. Concomitantly, T3 stimulates cell growth, as indicated by a 2-fold reduction in doubling time and a 2-fold increase in mitotic rate. The growth-stimulating effect has the same analog specificity and dose dependency as the morphological changes. The morphological changes could be potentially useful for evaluating the biological effects of T3 and its analogs and in studying the mechanism of thyroid hormone action.