Sialoadenectomy increases the concentration of immunoreactive epidermal growth factor in the mouse thyroid gland

The mouse thyroid gland contains significant concentrations of immunoreactive epidermal growth factor (EGF). To determine whether thyroidal EGF represents material obtained from the SMG via the circulation, we have compared EGF concentrations in sialoadenectomized (Sx) and sham-operated (Sh) BALB/c mice 30 days after surgical removal of the SMG. We found that the thyroids of Sx male and female mice had a significant increase in EGF concentration. The mean thyroidal EGF concentration (ng/mg wet weight) was 3.67 +/- 0.58 for Sx males, 1.53 +/- 0.47 for Sh males (p less than 0.02), 3.03 +/- 0.64 for Sx females, and 1.08 +/- 0.54 for Sh females (p less than 0.001), respectively. Thus EGF found in the mouse thyroid gland does not appear to arise from the SMG, and the thyroid appears to be an independent source of EGF synthesis.