Ontogenesis and distribution of epidermal growth factor immunoreactivity and binding activity in the mouse fetal and neonatal tissues.

Epidermal growth factor (EGF) immunoreactivity, EGF binding activity, and their ontogenic changes were investigated in placenta, amnion, and various organs of mouse fetus and neonate. EGF immunoreactivity was detected in all organs examined such as fetal and neonatal liver, brain, lung, intestine, placenta, and amnion. The fetal tissues having relatively higher EGF content were amnion, liver, and intestine. The tissue distribution of EGF immunoreactivity in the fetus did not differ from that in neonate. As for its ontogenesis, EGF immunoreactivity was almost constant during fetal development in liver, brain, and placenta, whereas it gradually increased in intestine. Scatchard plot analysis of EGF receptor, which was also demonstrated in all organs studied, revealed that EGF receptor in these tissues showed curvi-linear profile and its affinity was very high. Unlike EGF immunoreactivity, EGF binding activity showed tissue distributional difference between fetus and neonate except skin; EGF binding activity was relatively high in heart, kidney, lung, and intestine in the fetus, whereas it was high in liver, kidney, heart, and lung in the neonate. As for its ontogenesis, EGF receptor increased in liver as gestation proceeded, while it decreased in intestine. These results suggest that the biological importance of EGF in fetal development may be variable among fetal organs despite the ubiquitous existence of EGF and its receptor in many fetal tissues.