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. Author manuscript; available in PMC: 2015 Aug 1.
Published in final edited form as: Cancer Res. 2014 Aug 1;74(15):4099–4110. doi: 10.1158/0008-5472.CAN-13-3156

Figure 2.

Figure 2

Effect of dLEN versus LD 12:12 lighting schedules or administration of exogenous melatonin in the dLEN lighting schedule on the serum melatonin profile in female nude rats. Female nude rats with (ERα+) tissue-isolated breast tumor xenografts were housed under control (LD 12:12) or experimental, dLEN (with light at 0.2 lux) lighting schedules, or dLEN and supplemented with nighttime melatonin (MLT), and treated with diluent or 4OH-tamoxifen (TAM). (A) Diurnal plasma melatonin levels (pg/ml; mean ± 1 SD) of female nude rats maintained in a controlled LD 12:12 or experimental (dLEN) lighting cycle (n=12/group) were measured as described in “Materials and Methods”. Data are double-plotted to better visualize rhythmicity (n = 12/group). Significant differences (p < 0.05) in serum melatonin levels in rats under the different lighting schedules are denoted by an asterisk (*). (B) Plasma melatonin levels from Study II at 1200 hr (red bars) and 2400 hh (blue bars) from animals maintained in dLEN and treated with vehicle (dLEN Controls) or TAM (dLEN + TAM), or from animals on dLEN but supplemented with melatonin (in nighttime drinking water) and treated with vehicle (dLEN+TAM) or TAM (dLEN+TAM+MLT), as described in “Materials and Methods”. Significant differences (n=3/group, p < 0.05) in serum melatonin levels in rats under the different lighting schedules are denoted by an asterisk (*).