Quantitation of Epidermal Growth Factor in the Rat

Epidermal growth factor (EGF) was purified from the rat submandibular gland to establish a radioimmunoassay. Detectable amounts of EGF were found in the rat duodenum (medium, 0.55 pmol/duodenum; range, 0.38-0.68 pmol/duodenum; no. = 10) and duodenal juice (median, 215 pmol/l; range, 95-468 pmol/l; no. = 10), whereas no EGF was detected in the jejunal extracts. Submandibular and duodenal EGF each consisted of two isopeptides (pI 4.8, 5.4, and 5.5, 6.0 respectively). The peptides behaved alike both with regard to immunoreactivity (radioimmunoassay) and receptor binding (radioreceptor assay). The present data combined with previous results suggest a role for EGF in the gastrointestinal tract.