DEVELOPMENTAL-CHANGES IN AND HORMONAL MODULATION OF EPIDERMAL GROWTH-FACTOR CONCENTRATION IN THE RAT SUBMANDIBULAR-GLAND

Developmental changes in and hormonal effects on the concentration of epidermal growth factor (EGF) in the rat submandibular gland were inve stigated. The level of EGF in the gland gradually increased with age f rom 4 up to 8 weeks of age; thereafter it increased markedly, reaching a plateau level at 12 weeks ofage in both male and female rats. A sig nificant sex difference in EGF levels was observed between 8 and 14 we eks, the level in the males being approximately twice as high as that in the females at 12 and 14 weeks of age. Castration of male rats decr eased EGF to about the same level as that of control females. Treatmen t of castrated rats with testosterone propionate (TP) restored EGF to the levels in control male rats. Ovariectomy and/or administration of oestradiol-17 beta to ovariectomized rats had no apparent effect on EG F concentration.These findings indicate that the sex difference in EGF concentration can be attributed to the level of endogenous androgens. In addition, hypophysectomy ofmale rats caused a remarkable decrease in submandibular gland EGF to about 7%of the normal level. This reduct ion was significantly, although not completely, restored by the admini stration of TP, tri-iodothyronine (T-3) or GH. Moreover, giving TP wit h T-3 or with GH or both together had additive effects on the increase in EGF levels in hypophysectomized rats. These results provide eviden ce that EGF in the submandibular gland is regulated multihormonally by at least TP, T-3 and GH.