EFFECT OF THYROID HORMONES ON APOPTOSIS IN CHICK SKELETAL MUSCLE CELLS

点击翻译按钮获取中文摘要

Myoblasts were isolated from thigh muscles of 13-day-old chick embryos by digestion with dispase. After the cells were incubated for 24 hours, thyroid hormones -thyroxine (T4) and triiodothyronine (T3) - were added in the medium and the incubation was continued for 6 days. Cell differentiation was increased by both T4 and T3 while cell proliferation was inhibited by T3 but not by T4. Furthermore, muscle protein breakdown wasincreased and DNA content was decreased by T3 but not by T4. Thus DNA cleavage and fragmentation as indices apoptosis were measured and shown that apoptosis was induced by T3 but not by T4. Proteasome and cathepsin activities were also measured to show the relationship with apoptosis. The results indicated a possible relationship between apoptosis and protease activity. The present study shows that T4 is an active hormone but it's role is different from that of T3.