Melatonin enhances tamoxifen's ability to prevent the reduction in microsomal membrane fluidity induced by lipid peroxidation

J. J. García, R. J. Reiter, G. G. Ortiz, C. S. Oh, L. Tang, B. P. Yu, G. Escames

Research output: Contribution to journalArticlepeer-review

90 Scopus citations


The indoleamine melatonin and the synthetic antiestrogenic drug tamoxifen seem to have similar mechanisms in inhibiting the growth of estrogen receptor positive breast cancer cells. In this study, we compared the ability of these molecules, alone and in combination, in stabilizing microsomal membranes against free radical attack. Hepatic microsomes were obtained from male rats and incubated with or without tamoxifen (50-200 μM), melatonin (1 mM) or both; lipid peroxidation was induced by addition of FeCl3, NADPH and ADP. After oxidative damage, membrane fluidity, measured by fluorescence polarization techniques, decreased whereas malonaldehyde (MDA) and 4-hydroxyalkenals (4-HDA) concentrations increased. Incubation of the microsomes with tamoxifen prior to exposure to free radical generating processes inhibited, in a dose-dependent manner, the increase in membrane rigidity and the rise in MDA+4-HDA levels. When melatonin was added, the efficacy of tamoxifen in preventing membrane rigidity was enhanced. Thus, the IC50s for preventing membrane rigidity and for inhibiting lipid peroxidation obtained for tamoxifen in the presence of melatonin were lower than those obtained with tamoxifen alone. Moreover, tamoxifen (50-200 μM) in the presence of melatonin reduced basal membrane fluidity and MDA+4-HDA levels in microsomes. These synergistic effects of tamoxifen and melatonin in stabilizing biological membranes may be important in protecting membranes from free radical damage.

Original languageEnglish (US)
Pages (from-to)59-65
Number of pages7
JournalJournal of Membrane Biology
Issue number1
StatePublished - Mar 1 1998
Externally publishedYes


  • Antioxidant
  • Lipid peroxidation
  • Melatonin
  • Membrane fluidity
  • Microsome
  • Tamoxifen

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology


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