INVOLVEMENT OF THE IODOTHYRONINES IN LIVER AND HEPATOMA-CELL PROLIFERATION IN THE RAT

Abstract

3,3'',5-Triiodo-L-thyronine (200 .mu.g/100 g) was a potent liver parenchymal cell mitogen in the rat, and thyroidectomy severely inhibited hepatocyte proliferation in regenerating rat liver. Together, these observations point to a crucial role for the iodothyronine in liver cell hyperplasia. The growth rates of the transplantable Morris hepatomas 7777 and 5123tc were retarded in the surgically thyroidectomized-parathyroidectomized rat. This inhibition of tumor growth can be reversed by thyroid hormone administration. It has been observed earlier that the hypothyroid state induced in the rat by administration of propylthiouracil or radioactive iodine retarded the growth of the transplanted Morris hepatomas 7800 and 44, suggesting that these tumors were also thyroid dependent. The thyroid hormones may play a similar role in the growth of liver cell-derived cancers as they do in normal hepatocyte proliferation.