THE EFFECTS OF METHIMAZOLE ON HEMATOPOIESIS IN MICE

The effects of anti-thyroid drug, methimazole (MMI), on haematopoiesis in inbred C57BL/6 mice were studied. The in vitro proliferative respo nse of bone marrow (BM) cells to interleukin-3 (IL-3) was significantl y increased when mice were provided with 0.1% MMI in water (w/v) ad li brium for 4 to 6 weeks. Using soft agar agar colony assay, the numbers of myeloid cell colonies were also significantly increased in mice tr eated with MMI. However, the proliferative response of BM cells to IL- 3 was found to be greatly reduced 10 weeks after MMI treatment. In vit ro studies showed that MMI alone at the concentrations of 500 mu M or above inhibited both the growth of normal BM cells in liquid culture: and the formation of macrophage (M) - / granulocyte (G) - colonies in soft agar culture in a dose dependent Direct cytotoxic effect of MMI ( 0 - 1250 mu M) to normal BM cells was not Results from this study sugg ested that MMI can modulate the development of myeloid haematopoietic cells.