ERYTHROPOIETIN-INDUCED ULTRASTRUCTURAL ALTERATIONS TO J2E CELLS AND LOSS OF PROLIFERATIVE CAPACITY WITH TERMINAL DIFFERENTIATION

Erythropoietin (epo) induced differentiation of the J2E erythroid cell line is characterized by haemoglobin synthesis, together with morphol ogical changes and an immediate increase in proliferation In this manu script we have shown that the size of J2E cells decreased during diffe rentiation and the nucleus to cytoplasm ratio was reduced appreciably. Furthermore, major ultrastructural alterations occurred-mitochondria, rough endoplasmic reticulum and Golgi apparatus decreased in size and number with maturation, while nuclei condensed considerably before ex trusion. The use of mitotic indices, H-3-thymidine uptakes and flow cy tometry confirmed that the immature J2E cells undergo enhanced replica tion shortly after epo stimulation. In addition, we demonstrated that cell division ceased as the cells entered the final stages of erythroi d differentiation. Thus the J2E line provides a useful model, not only for haemoglobin synthesis, but for all aspects of erythroid terminal differentiation.