EPITHELIAL-CELL PROLIFERATION IN THYMIC HYPERPLASIA INDUCED BY TRIIODOTHYRONINE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 27  (3) , 516-521
Abstract
A significant hyperplasia of the thymus was induced in mice, treated with triiodothyronine [T3] during the 1st mo. of life. Stereological data showed that, in both treated and control mice, mononucleate epithelial cels were 4 times more numerous in the medulla than in the cortex. After T3 treatment, their absolute number in both cortex and medulla increased 2-fold. The number of thymic epithelial cells could be regulated by thyroid hormones. The cortical volume in treated mice was also twice that of controls but medullar volume showed an increase of only 50%. Cortical epithelial cells increased at the same rate of the cortex volume but medullary epithelial cells grew more rapidly. In fact the medullary volume enlargement could be explained mainly by the growth of the epithelium. Medullary lymphocytes did not proliferate in the same way as cortical lymphocytes after thyroid hormone administration. The recently described multinucleate epithelial cells were not modified in number and were insensitive to thyroid hormones.