The addition of EGF and bombesin to both ras-induced and differentiated cells did not induce Ca2+ mobilization, suggesting that the cells may not have receptors for the ligands, or desensitization of the receptors may have occured by a different signalling pathway such as stimulation of protein kinase C activity. | Tr. J. of Biology 23 (1999) 159-168 © TÜBİTAK Cytosolic Ca2+ levels in CO25 myoblast cells bearing a human N-ras oncogene after stimulation by thapsigargin and growth factors Hülya ZEYTİNOĞLU University of Anadolu, Faculty of Science, Department of Biology, 26470 Eskişehir-Turkey Ian GIBSON University of East Anglia, School of Biological Sciences, NR4 7TJ Norwich, UK. Received: Abstract: The levels of intracellular calcium [Ca2+ ]i were examined in CO25 myoblast cells bearing a mutated human N-ras oncogene, after stimulation by thapsigargin (ThG), bombesin and epidermal growth factor (EGF). Thapsigargin induced a [Ca2+ ]i rise mostly from intracellular calcium pools, and a small Ca2+ entry into cytoplasm via the plasma membrane channel. In both ras-induced and differentiated CO25 cells, [Ca2+ ]i increase showed a similar pattern of events after addition of ThG. 2+ The addition of EGF and bombesin to both ras-induced and differentiated cells did not induce Ca mobilization, suggesting that the cells may not have receptors for the ligands, or desensitization of the receptors may have occured by a different signalling pathway such as stimulation of protein kinase C activity. Key Words: N-ras, myoblast, [Ca2+ ]i, thapsigargin, EGF, bombesin. İnsan N-ras onkogeni taşıyan CO25 miyoblast hücrelerinde thapsigargin ve büyüme faktörleri ile stimülasyonlarından sonra hücre içi Ca2+ seviyeleri Özet: CO25 miyoblast hücrelerinin, thapsigargin (ThG), bombesin ve epidermal büyüme faktörü (EGF) 2+ ile stimülasyonları sonucunda hücre içi kalsiyum [Ca ]i seviyeleri araştırılmıştır. ThG, çoğunlukla hücre içi kalsiyum depolarından salınması ve az miktarda plazma zarı kanallarından Ca2+ girişi yoluyla bir [Ca2+ ]i artışına neden olmuştur. Ras geninin aktif olduğu yada farklılaşmış CO25 hücrelerinin her ikisinde de ThG nin hücre içi Ca2+ iyonlarının yükselmesi üzerine etkisi benzer bir şekilde olmuştur. EGF ve bombesinin, ras geninin aktif olduğu yada farklılaşmış .
