Epidermal growth factor in mice: changes during circadian and female reproductive cycles

To clarify the variation of mouse epidermal growth factor production during the 24-h and female reproductive cycles, we measured its concentrations in the plasma, submandibular salivary gland, urine, kidneys and liver of adult male and female mice during consecutive 12-h dark and 12-h light periods, different stages of pregnancy, and lactation. The concentration of epidermal growth factor in the submandibular gland showed no circadian changes. In plasma and in the liver it increased during the dark period, whereas in urine and in the kidneys it peaked in the daytime. In the submandibular gland the concentration decreased during early pregnancy, but it returned to the non-pregnant levels by mid-pregnancy. In plasma it decreased progressively during pregnancy and recovered during lactation. In urine and the kidneys the concentration of epidermal growth factor increased after early pregnancy; with a further great increase in the kidneys during lactation. In the liver the concentration was clearly below the non-pregnant levels during late pregnancy and lactation.