Radioimmunoassay of Human Epidermal Growth Factor (Urogastrone)1

Abstract

Epidermal growth factor (EGF) is a polypeptide hormone that stimulates growth of a variety of tissues. Although it was originally discovered in male mouse submaxillary glands, EGF has recently been isolated from human urine. A heterologous radioimmunoassay for human EGF (hEGF) has been developed, using purified hEGF as reference standard and radioiodinated tracer and antibodies raised against mouse EGF. Purified hEGF specifically displaced radioiodinated hEGF from the antibodies; no other human peptide hormone tested demonstrated any cross-reaction. Twenty-four hour urinary excretion of RIA-hEGF in normal adult males and females was 97.8 ± 10.7 and 72.0 ± 4.5 (mean ± SE) μg/total volume, or 51.7 ± 4.5 and 57.0 ± 4.9 μg/g of creatinine, respectively. Urinary excretion in normal children increased with age, from less than 40 μg/24 h at 4 years of age to adult levels at about the age of puberty. The concentration of RIA-hEGF in human saliva ranged from 5.6 to 16.8 ng/ml, was about 80 ng/ml in human milk and was undetectable in human amniotic fluid (<1.4 ng/ml). It has recently been suggested that human EGF is identical with human urogastrone. However, the tissue secreting this “new” human hormone and the role of hEGF in health and disease have yet to be determined.