EGF content in the gastrointestinal tract of rats: effect of age and fasting/feeding.

Immunoreactive rat epidermal growth factor (EGF) was measured in the pancreas and in the mucosa and lumen of the stomach, duodenum, jejunum, midjejunum, ileum, and colon of fed or fasted 5- and 12-day-old suckling, and 3- to 4-month-old adult male rats using a homologous radioimmunoassay. The EGF levels in the pancreas in sucklings were lower than in adults and were unaffected by fasting. Both gastrointestinal mucosal and luminal EGF levels were higher in suckling rats than in adults. Fasting caused a significant decrease in gastrointestinal levels of EGF in the suckling rats but resulted in minimal changes in the adults. Our results show that the content of EGF in gastrointestinal tract is dependent on both age and dietary status. Together with the fact that milk contains a large amount of EGF (O. Koldovský and W. Thornburg, J. Pediatr. Gastro. Nutr. 6: 172-196, 1987) and that labeled EGF is absorbed to a considerable extent by the gastrointestinal tract of suckling rats (P.A. Gonella et al., J. Clin. Invest. 80: 22-32, 1987: W. Thornburg et al., Am. J. Physiol. 246: G80-G85, 1984), our present study implicates milk as an important source of EGF in the suckling period.