title: Melatonin effect on the ultrastructure of Ehrlich ascites tumor cells, lifetime and histopathology in Swiss mice.
abstract: OBJECTIVE
  One of the models used for studying cancer is the Ehrlich ascites tumor (EAT) due to its ability to grow in liquid suspension, allowing a standard number of cells to be inoculated, growth quantification and regression of tumor mass. Among the oncostatic substances, melatonin has shown effectiveness in limiting the tumor cell proliferation. However, studies have shown contradictory effects of melatonin on the EAT. This study has investigated the melatonin effect on tumor growth, time and survival percentage, ultrastructure and metastasis of EAT cells in mice submitted or not to pinealectomy.
  
  
  METHODS
  Animals were inoculated with 5×106 cells/mL and treated or not with exogenous melatonin with doses of at 150 and 300 μg/30 g animal weight for 12 days. Melatonin significantly reduced the abdominal circumference, volume of ascites liquid and EAT-cell viability, raising rates of time and mice survival percentage.
  
  
  RESULTS
  Ultrastructurally, the melatonin treatment revealed changes in the shape of cells, the cell surface showed numerous projections, some bifurcated, cytoplasmic vacuolation, mitochondrial degeneration and nuclear fragmentation, peculiar characteristics of apoptosis. Histopathology revealed no metastasis in the liver, small intestine and large intestine in any of the animals in the experimental groups; however this process was evident in the lungs and kidneys, being inhibited by melatonin administration.
  
  
  CONCLUSIONS
  Thus,we can conclude that doses of 150 and 300μg/30g of melatonin for 12 consecutive days have a very effective oncostatic and cytotoxic activity on EAT cells in mice.
authors.forename: Ana Paula C
authors.initials: AP
authors.lastname: Batista
authors.forename: Terezinha G
authors.initials: TG
authors.lastname: da Silva
authors.forename: Álvaro A C
authors.initials: ÁA
authors.lastname: Teixeira
authors.forename: Paloma L
authors.initials: PL
authors.lastname: de Medeiros
authors.forename: Valeria W
authors.initials: VW
authors.lastname: Teixeira
authors.forename: Luiz C
authors.initials: LC
authors.lastname: Alves
authors.forename: Fábio A B
authors.initials: FA
authors.lastname: dos Santos
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002286:Carcinoma, Ehrlich Tumor / Q000188:drug therapy* / Q000473:pathology / Q000648:ultrastructure; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008550:Melatonin / Q000008:administration & dosage / Q000494:pharmacology*; D051379:Mice; D009362:Neoplasm Metastasis; D010870:Pineal Gland / Q000601:surgery; D015996:Survival Rate
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; D008550:Melatonin