EFFECT OF ENDOTHELIN-1 AS GROWTH-FACTOR ON A HUMAN GLIOMA CELL-LINE -ITS CHARACTERISTIC PROMOTION OF DNA-SYNTHESIS

In addition to its powerful vasoconstrictive activity, endothelin-l (E T-1) has been recognized to stimulate DNA synthesis in some cell lines . In this study, we confirmed the existence of ET-1 receptor in YKG-1 human glioma cells, and investigated its effect on DNA synthesis in YK G-1 for 6 consecutive days, comparing it with that of epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and insulin-like growth factor-I (IGF-I). Scatchard analysis of the binding data revea led the presence of a single class of high-affinity binding molecule. The apparent dissociation constant (Kd) was 5.2 x 10(-9) M and the max imal binding capacity (B max) was 4.7 x 10(4) sites/cell. The percenta ge of non-cycling cells was initially more than 85 %, and decreased to 55.40 %, 24.22 %, 11.50 %, and 7.51 % on days 1, 2, 4, and 6, respect ively, after ET-1 stimulation. Although ET-I reduces the fraction of n on-cycling cells more slowly than other growth factors such as EGF, PD GF and IGF-I, it reaches the same level as the others by day 6. These results indicate that YKG-1 human glioma cells have ET-1 receptors and that ET-1 initiates a peculiar slow induction of DNA synthesis in the se cells, suggesting that secondary factors might exist to accelerate the DNA synthesis in response to ET-1.