The influence of thyroidectomy and of triiodothyronine administration on epithelial cell proliferation in the jejunum of rat.

Mitotic rates in epithelial cells lining the bases of the crypts of Lieberkühn in rat jejunum were measured using a stathmokinetic technique. Two weeks after surgical thyroidectomy the mitotic rate in the jejunal crypt cells was significantly lower than that in control animals. During the four hour period immediately after injection of triiodothyronine into thyroidectomized rats the crypt cell mitotic rate was significantly higher than in control animals.