Figure 5. Effect of melatonin on CFU-MK, CFU-F and CHRF cells. Bone marrow cells were seeded with or without melatonin (200 nM) for nine days and identified by Giemsa staining. CHRF cells were treated with melatonin (200 nM), wortmannin (100 nM), melatonin+wortmannin, luzindole (1 μM) and melatonin+luzindole. A 30 min preincubation step with the PI3K inhibitor Wortmannin (100 nM) or a 60 min preincubation step with the MT2 receptor antagonist Luzindole (1 μM) was included before melatonin stimulation. (A) Melatonin promotes the formation of murine CFU-MK and CFU-F. (B) Melatonin has a promoting effect on the proliferation of CHRF cells, adding wortmannin and luzindole can inhibit this effect. Two-way ANOVA (with a Tukey multiple comparison test) was employed to test for significance. * p< 0.05, ** p< 0.01, n=4. CFU-MK, colony- forming unit-megakaryocyte; CFU-F, colony forming unit- fibroblast.