Mitosis in the oesophageal epithelium of rats during chronic antithyroid treatment with carbimazole

Abstract

ABSTRACT The mitotic activity of the oesophageal epithelium of male rats maintained under carefully controlled conditions was studied, using the metaphase-arrest agent, vincristine sulphate. The accumulation of metaphases was linear (r = 0·97). In untreated rats there was a clear mitotic rhythm with a peak metaphase index (expressed as a percentage) of 12·4±0·86 (s.e.m.) at 12.00–15.00 h and a trough of 1·3±0·35 at 24.00 h. The overall mean metaphase index was 5·4±0·76. The effect of treatment with the antithyroid agent, carbimazole (0·1 g/100 ml in the drinking water), for 3 weeks was to depress the higher values at 12.00–18.00 h (P <0·01), while leaving the overall index unchanged. Carbimazole caused a significant (P <0·01), transient 40% increase in the metaphase index after 2 days; thereafter the metaphase index remained at control levels until 12 weeks of treatment when a steady decline occurred until 24 weeks. The results are in contrast to those in previously described experiments on thyroid follicular cells which show a large increase in the first few days of treatment, followed by a steady decline towards control levels at 12 weeks. The metabolic activity of the animals is about 50% of normal at 12 weeks when both the oesophageal epithelium and the thyroid follicular cells begin to show a reduction in proliferative activity. Journal of Endocrinology (1990) 127, 311–315