Hormonal modulation of mouse plasma concentration of epidermal growth factor

To understand the physiological role of plasma epidermal growth factor (EGF) we studied in adult female mice the effect of endocrine manipulations on serum EGF concentration (S-EGF). Starting 1 month after sham operation (sh) or excision (SX) of the submandibular salivary gland (SMG), groups of 6 mice were given sc injections of T4 (0.4 micrograms/g daily), testosterone propionate (TP, 25 micrograms/g every 48 h), T4 + TP, or SMG extract (20 micrograms EGF daily) for 10 days. They were exsanguinated via the abdominal vena cava on day 11. During treatment the SX mice gained 55% less weight and their S-EGF was 25% lower compared with the sh mice. Hormone effects were clear in the SX mice: T4 caused a 35% decrease in S-EGF and a 5-fold increase in SMG-EGF concentration. TP caused a 1.6-fold increase in S-EGF and a 6-fold increase in SMG-EGF. Twenty-four hours after the last injection of SMG extract S-EGF remained 1.6-fold elevated. We conclude that plasma EGF is largely independent of SMG, and is modified by hormones in ways different from known tissue effects. This is consistent with an endocrine role of EGF.