Age related changes in immunoreactive epidermal growth factor concentrations in murine thyroid and submaxillary...

Extracts from the thyroid and submaxillary glands (SMG) of neonatal (7 days), adult (2-3 mo), and senescent (8-10 mo) BALB/c mice were analysed for possible age related changes in immunoreactive (IR) mouse epidermal growth factor (mEGF) concentration. Immunoreactive mEGF was undetected (less than 0.01 ng/mg weight) in the SMG of 7 day-old male and female mice but the levels (mean +/- S.E) increased to 6.77 +/- 1.27 micrograms/mg (males) and 57.60 +/- 7.12 ng/mg (females) at the age of 2-3 mo, and declined significantly to 2.64 +/- 0.34 micrograms/mg (males) and 26.80 +/- 3.16 ng/mg (females) at the age of 8-10 mo (P less than 0.001). In the thyroid, IR-mEGF concentrations (ng/mg weight) were similar in 7 day-old (1.27 +/- 0.38 in males and 1.96 +/- 0.61 in females) and in 2-3 month old mice (2.20 +/- 0.51 in males and 1.50 +/- 0.42 in females) but decreased significantly (P less than 0.001) in 8-10 month old mice (1.06 +/- 0.21 in males and 0.54 +/- 0.18 in females). Since the concentration of IR-mEGF in the thyroid glands of 7 day-old mice already approached adult levels while none was detectable in their SMG, EGF may have a physiological role in thyroid regulation.