FIGURE 4.

Effects of melatonin on radiation-induced changes on aromatase activity and expression and aromatase promoter 1.7 mRNA expression in endothelial cells. HUVECs treated for a week with melatonin 1 mM or its diluent were co-cultured with MCF-7 cells as indicated in see section “Material and Methods.” (A) When a homogenous monolayer of pre-confluent HUVECs was reached, media were aspirated and changed to serum-free media containing the labeled substrate 300 nM [1β-3H(N)]-androst-4-ene-3,17-dione and irradiated. After 24 h of incubation, aromatase activity was measured as described in material and methods. (B,C) Control and melatonin pretreated endothelial cells were irradiated and incubated for 4 h. The total cellular RNA was isolated from cells and reverse transcribed. cDNA was subjected to PCR using specific primers for aromatase and aromatase promoter 1.7 or S14. Data are expressed as the percentage of the control group (Mean ± SEM). C, control; M, melatonin; and R, radiation. a, p < 0.001 vs C (HUVEC); b, p < 0.05 vs C (HUVEC); c, p < 0.001 vs R (HUVEC); d, p < 0.05 vs C (HUVEC/MCF-7); e, p < 0.001 vs C (HUVEC/MCF-7); and f, p < 0.05 vs R (HUVEC/MCF-7).