Table 2.

Tumor levels of total cAMP in response to increasing light intensities during darkness

Light intensity (μW/cm2)Tumor cAMP concentration (nmol/g)
Rat hepatoma 7288CTCSR MCF-7 human breast cancer xenografts
Dark0.18 ± 0.010.02 ± 0.0
0.020.45 ± 0.06 *0.09 ± 0.01
0.050.50 ± 0.06 *0.27 ± 0.01
0.060.53 ± 0.03 *0.26 ± 0.03
0.080.48 ± 0.03 *0.31 ± 0.04
Constant light, 3450.72 ± 0.04 0.33 ± 0.03 §
  • NOTE: Effects of exposure of rats bearing either hepatoma 7288CTC (male rats) or SR MCF-7 human breast cancer xenografts (nude female rats) to increasing intensities of light during the entire dark phase (12 hours) of a 12-hour light/12-hour dark cycle on tumor cAMP concentrations. At the end of the growth period for each of the light treatment groups, tumors were freeze-clamped under liquid N2 and then assayed for cAMP via an ELISA. See Figs. 2 and 3 legends for further details. Value are means ± SE; n = 6 rats (tumors per group).

  • * P < 0.05, hepatoma vs dark control.

  • P < 0.05, breast vs dark control (except 0.08 μW/cm2).

  • P < 0.05, hepatoma vs all other groups.

  • § P < 0.05, breast vs all other groups (except 0.08 μW/cm2).