MITOTIC RATE OF THYROID FOLLICULAR CELLS IN UNTREATED AND GOITROGEN-TREATED RATS - VARIATION WITH TIME OF DAY

  • 1 January 1979
    • journal article
    • research article
    • Vol. 129  (DEC) , 731-741
Abstract
The results of investigations into the mitotic rates of thyroid follicular cells of adult male rats maintained under controlled conditions of temperature, photoperiod and handling are presented. The mitotic rate in 8 successive 3 h periods of the day showed a clear mitotic rhythm, with a maximum at 1200-1500 h in untreated rats. The mitotic rate over the 24 h period was 7.6 .+-. 0.83 (SE) metaphases/10,000 cells per h. Rats treated with the antithyroid drug, carbimazole, for 3 wk were manifestly hypothyroid, as shown by decreases in O2 consumption and growth rate. With carbimazole the mitotic rate of the thyroid follicular cells was increased 3-fold and the mitotic rhythm was no longer detectable. In an experiment to test the efficiency of vincristine sulfate, the accumulation of metaphases after 1 mg/kg or 2 mg/kg vincristine was linear for 0.5-8 h, although, at the higher dose, the number of metaphases was reduced after 8 hours. The mean daily rate in untreated rats was approximately commensurate with the rate of increase of body weight, which supports the classification of follicular cells as an expanding cell population.