抄録
In order to investigate the effects of vitamin A (VA) supplementation on thyroid proliferative lesions associated with goitrogens other than thiourea, F344 rats were given VA in the diet at 0.1% and drinking water containing sulfadimethox-ine, propylthiouracil, potassium thiocyanate or phenobarbital for 19 weeks after initiation with N-bis (2-hydroxypropyl) nitrosamine. At the end of the treatment period, serum T3, T4, and TSH levels, T4-uridinedi phosphate glucuronosyltransferase (UDP-GT) activity in the liver, and thyroid weights were determined. In addition, thyroid proliferative lesions were histologically examined and evaluated for their PCNA labeling indices. Although serum T4 levels were lowered by VA in all goitrogen-treatment cases, serum levels of TSH, which is responsible for control of proliferation of thyroid follicular cells, were not elevated by the VA supplementation. There were also no enhancing effects of VA in terms of the other parameters, suggesting that the enhancement observed ealier with thiourea is a special case.
