The influence of thyroid and testicular hormones on the epithelium of crypts of Lieberkühn in the rat's intestine.

Abstract

AbstractThe growth of duodenal crypts of Lieberkühn was investigated in male Sherman rats subjected to thyroidectomy, and/or castration. Histological sections were studied, counting interphase nuclei and mitoses in 25 longitudinally sectioned crypts per animal. At 49 gm body weight, initial control animals had an average of 65.8 ± 2.4 cells per crypt section, and 80 days later, sham‐operated controls weighed 269 gm and had 91.4 ± 5.1 cells per crypt section. There were only 75.0 ± 3.7 cells per crypt section 80 days after thyroidectomy, while castrates had 97.0 ± 2.6 cells per crypt section. Thyroidectomy combined with castration produced results similar to thyroidectomy alone, 74.0 ± 2.5 cells per crypt section. Treatment of such doubly operated rats with testosterone during the last 42 days of the experiment significantly increased the cell number, to 82.7 ± 2.8 per crypt section, while thyroxine increased it to 100.8 ± 4.3. Thus, in the rat, the number of cells per crypt increases between juvenile and adult stages, and this growth is subject to endocrine regulation, particularly by the thyroid.The mitotic index of crypt cells increases with age, from 3.9 ± 0.1% at 49 gm body weight, to 5.2 ± 0.3% at 269 gm body weight. Castration did not interfere with this increment, but it was reduced in the absence of thyroid hormone, and was restored by the injection of thyroxine to thyroidectomized castrates.Finally, from related observations in previously reported and unpublished experiments, it is suggested (1) that the influence of thyroid hormone on crypt cell number may be mediated, at least in part, through an action on growth hormone release from the anterior pituitary and (2) that the rate of change in cell number with age may be determined in some measure by a change in the rate of cell displacement toward the villus tip, in addition to a change in mitotic index.