title: Effects and mechanisms of melatonin on immune responses in mice of different months.
abstract: OBJECTIVE
  To study the effects and mechanisms of melatonin (MT) on immune responses in mice of different months.
  
  
  METHODS
  Thymocyte proliferation and IL-2 activity were assayed by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) and activated mouse splenocyte proliferation methods, respectively; cAMP and methionine-enkephalin (met-Enk) level was determined by competitive protein binding assay and radioimmunoassay, respectively.
  
  
  RESULTS
  The function of lymphocytes, obtained from BALB/c mice aged 6 and 11 months were decreased, which was restored by melatonin at the dose of 5 mg/kg or 30 mg/kg. In vitro, proliferation of lymphocytes in 11-month-old mice was decreased and cAMP level was increased. Melatonin (0.1 nmol/L or 1 micromol/L) had negative regulation to this. Forskolin (10 micromol/L) enhanced the cAMP level of lymphocytes in 2- and 11-month-old mice (P<0.01), which was antagonized partially by melatonin and this effect of melatonin was also abolished by pertussis toxin (1 mg/L) completely. Melatonin (1 micromol/L and 0.1 nmol/L) increased the content of met-Enk of lymphocytes in 2- and 11-month-old mice, respectively (P<0.01), which was blocked by nifedipine (1 micromol/L).
  
  
  CONCLUSIONS
  Melatonin exerted an effect on immune responses in mice of different months, which might be mediated by G protein-AC-cAMP signal transduction pathway and regulation of met-Enk level.
authors.affiliation: Institute of Clinical Pharmacology, Anhui Medical University, Hefei 230032, China. wwei@ahmu.edu.cn
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Yu-Xian
authors.initials: YX
authors.lastname: Shen
authors.forename: Min
authors.initials: M
authors.lastname: Dai
authors.forename: Qun
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000367:Age Factors; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002469:Cell Separation; D000242:Cyclic AMP / Q000096:biosynthesis; D004744:Enkephalin, Methionine / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D007109:Immunity / Q000187:drug effects* / Q000276:immunology; D007376:Interleukin-2 / Q000096:biosynthesis; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology; D008550:Melatonin / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D051381:Rats; D015398:Signal Transduction
chemical_list: D000276:Adjuvants, Immunologic; D007376:Interleukin-2; D004744:Enkephalin, Methionine; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D008550:Melatonin