Methimazole slows hepatocyte streaming in rats.

Hepatocytes are hypothesized to continually stream from the portal tract to the terminal hepatic vein. By this model, when a cell divides, one of its progeny replaces the dividing ancestor and the other is displaced into a more remote location. The present experiment aims to demonstrate that hypothyroidism affects liver cell turnover. Thirty male adult rats were divided into two groups. One received methimazole for two weeks and the other served as control. Each rat was injected intraperitoneally with 18.5 KBq [3H]thymidine/g body weight. Rats were killed after 1 hr and two and four weeks. Autoradiography was done. The distance of the labeled cells from the portal tract was measured. The mean TSH levels of the methimazole-treated group and controls were 1.45 and 0.25 mM/liter, respectively (P < 0.01). Hepatocyte streaming was lower in hypothyroid (1.8 microns/day) than in untreated rats (2.5 microns/day) (P < 0.01). The respective labeling indices 1 hr after labeling were 0.9% and 1.24% (P < 0.05). We conclude that hypothyroidism diminishes hepatocyte and littoral cell turnover and slows down their streaming.