ONTOGENESIS OP HEPATIC EPIDERMAL GROWTH FACTOR (EGF) METABOLISM IN NORMAL BALB MICE

Abstract

To characterize the ontogenesis of the hepatic EGF system in normal Balb mice, we measured serum and liver concentrations of EGF, and liver concentrations of pre-pro EGF mRNA and EGF receptor binding. Male and female animals were studied at 1, 2, 3, 5, 7 and 10 wks of life. After sacrifice, body weight and length were measured and serum and liver tissues were collected for EGF determinations. Immunoreactive serum EGF (mean ± SEM) increased at 7 and 10 wks and was significantly higher (p<0.05) in males (465± 53 and 683±120 pg/ml) than females (188±52 and 235±64 pg/ml). Liver EGF concentrations were low at 1, 2, 3 and 5 wks, significantly increasing (p<0.01) at 10 wks to 268±50 and 179±36 pg/μg protein for males and females (males versus females p<0.05 at 10 wks). EGF receptor binding of 125I-EGF was low at 1, 2 and 3 wks increasing to 5.03±0.83 and 5.79±1.02 (fm/μg membrane protein) in males and 1.84±0.64 and 2.36±0.28 in females at 5 and 10 wks respectively. Values were significantly lower (p<0.01) in females. Pre-pro EGF mRNA was examined at 1, 2, 3, 5, 7 and 10 wks. EGF message increased in liver to highest values at 10 wks in both males and females. Conclusions: There is a parallel increase of serum and liver EGF concentrations, and liver EGF mRNA between 5 and 10 wks of postnatal life. EGF receptor binding also increases during this time. The results suggest that newborn liver may be an important source of circulating EGF in Balb mice.