Hormonal modulation of mouse plasma concentration of epidermal growth factor

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Abstract
To understand the physiological role of plasma epidermal growth factor (EGF), the effect of endocrine manipulations on serum EGF concentration (S-EGF) was studied in adult female mice. Starting 1 mo. after sham operation (sh) or excision (SX) of the submandibular salivary gland (SMG), groups of 6 mice were given s.c. injections of T4 [thyroxine] (0.4 .mu.g/g daily), testosterone propionate (TP, 25 .mu.g/g every 48 h), T4 + TP or SMG extract (20 .mu.g 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 increased 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. Apparently 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.