Influence of experimental hyperthyreosis on hepatocytes' cell cycle in white mice

The thyroid hormones play the essential regulatory role in the process of hepatocyte proliferation and polyploidization. T3 has been shown to be a powerful inducer of hepatocyte proliferation in the rats. Although T3 is known to have a strong mitogenic effect on hepatocytes in vivo, little is known about long-term effects of thyroid hormone on liver parenchyma. Here we have studied the effect of thyroid hormone on the cell cycle of hepatocytes in white mice during experimental hyperthyreosis. The experiments were performed on 74 white mice, distributed in three age groups (juveniles, adults, senescents). Experimental hyperthyreosis was induced by injections of L-thyroxine (50 mcg/1 kg body weight). The method of flow cytometry was used. The results obtained allowed us to clarify the predominant role of thyroid hormones in the regulation of hepatocyte cell cycle. The significant role of the hyperthyroid status on liver polyploidization was evident. However, this effect seems to be age dependent. According to our data, hyperthyreosis in juveniles increases the degree of ploidity, whereas in adult and senescent mice--decreases. On the other hand, under action of hyperthyroid status the amount of apoptotic nuclei decreases in juveniles and increases in adults and senescents.