Aim To investigate the influences of melatonin (MT) on the growth of HeLa cells in vitro. Methods Theantiprolfferation activities of MT were evaluated in HeLa cells by means of trypan blue dye exclusion and MTT vital staining.The morphological changes of HeLa cells induced by MT were observed under transmission electronic microscope. Cell divisioncycle influenced by MT was assessed by a flow cytometry. Results MT produced a certain inhibition of HeLa cells at the con-centration of 2 mmol@ L-1 and prolonged the TD. The fraction of cells inhibited was 61.0%. The IC. so of HeLa cells exposed toMT for 96 h was 2.039 mmol@ L- 1. The flow cytometric analyses showed that exposure to MT for 72 h reduced the number ofHeLa cells in phase S. Under electronic microscope, the HeLa cells exposed to MT for 72 h displayed morphological changesof necrosis, apoptosis, more hetero-chromosome and less somatic chromosome. Conclusion MT showed certain influences onthe growth of HeLa cells. Its mechanism may probably be attributable to reduction of the number of cells in phase S.
