DIETARY IODINE AFFECTS EPIDERMAL GROWTH-FACTOR LEVELS IN MOUSE THYROID AND SUBMAXILLARY-GLANDS

To determine whether dietary iodine intake affects the levels of immun oreactive epidermal growth factor (EGF) in vivo in two mouse tissues k nown to be thyroid hormone responsive, 24 adult BALB/c mice were rando mized into groups of six animals and fed a) an iodine-deficient diet, b) normal laboratory chow(controls), c) an iodine-deficient diet with high physiological iodine supplementation (similar to 300 mu g/day), a nd d) an iodine-deficient diet with pharmacological doses of iodine (s imilar to 3mg/day). After 21 days on the various regimens, the mice we re killed and the concentration of mouse (m)EGF in the thyroid and sub maxillary glands (SMG) measured by radioimmunoassay. The mean (+/- SEM ) SMG mEGF level (mu g/mg wet weight) in the different groups were : a ) 7.58 +/- 1.87, b) 12.46 +/- 4.7, c) 19.79 +/- 4.47, and d) 24.36 +/- 5.96. The thyroid mEGF concentrations (ng/mg wet weight) were : a) 3. 65 +/- 0.75, b) 5.23 +/- 1.84, c) 8.07 +/- 1.18, and d) 6.43 +/- 0.95, respectively. Analysis of variance revealed that dietary iodine statu s had a significant effect on mEGF levels in both the SMG (p< 0.001) a nd the thyroid gland (p< 0.001). Compared to controls, tissue mEGF lev els decreased by 30-40% in the mice fed an iodine-deficient diet, and increased by 60-150% following physiologic iodine replacement.