Circadian rhythm of VEGF expression in the liver of hepatectomized-tumor-bearing adult and young mice

We analyzed VEGF expression in regenerating liver (after partial hepatectomy) of tumor-bearing adult and young mice, throughout one complete circadian cycle. The animals were sacrificed every 4 h, from 26 to 46 h post-hepatectomy. Liver samples were processed for immunohistochemistry. The results showed circadian variation of VEGF expression in hepatectomized mice (control group) and hepatectomized-tumor-bearing mice. The maximum value of VEGF expression was found at 16: 00/30 h of day/hour post-hepatectomy (HD/HPH) in tumor-bearing young mice, and at 20: 00/34 HD/HPH in the controls. In adult mice the maximum values of VEGF expression were at 16: 00/30 HD/HPH in tumor-bearing mice, and at 08: 00/46 HD/HPH in the controls. Young tumor-bearing mice showed significantly higher mean values than the controls. In conclusion, the presence of the tumor in the animals induces modifications in the intensity and the temporal distribution of the circadian curves of VEGF expression.