SISTER-CHROMATID EXCHANGES IN LYMPHOCYTES FROM METHIMAZOLE-INDUCED HYPOTHYROID MICE

The inhibitory effect of an antithyroid drug on mouse T lymphocytes wa s investigated. Inbred C57BL/6 mice were provided with an antithyroid drug, methimazole, for 2, 4 and 6 weeks and the in vitro responses of the lymphocytes were studied. The proliferative responses of T lymphoc ytes from the spleen of methimazole (MMI)-treated mice significantly ( p < 0.05) decreased following concanavalin A stimulation, and the inhi bitory effect became prominent with the increased duration of MMI trea tment. A concomitant increase in the frequency of induced sister-chrom atid exchanges was also observed in these T lymphocytes. When the sple nocytes were stimulated with concanavalin A for 24 h, their ability to produce interleukin-2 (IL-2) was significantly decreased (p < 0.05). The results indicated that methimazole interfered with the normal prol iferation of T lymphocytes by suppressing the production of IL-2, a cy tokine also known as T cell growth factor, as well as inducing a highe r incidence of sister-chromatid exchange during cell division.