Human urogastrone and mouse epidermal growth factor share a common receptor site in cultured human fibroblasts

Abstract The biological activity and receptor affinity of human beta-urogastrone (B-URO) was measured in cultured human fibroblast monolayers and compared with parallel measurements of the action and receptor affinity of mouse epidermal growth factor (m-EGF). B-URO stimulates both DNA synthesis and the uptake of the amino acid analogue, alpha-aminoisobutyric acid with high potency (ED 50 , 80±30 pM) in a concentration-dependent manner comparable to that of m-EGF. In the linear portion of the dose-response curve, the effects of B-URO and m-EGF are additive; at maximally active concentrations of B-URO, no further stimulation is observed on adding m-EGF. Measurements of the binding by fibroblasts of 125 I-labelled B-URO indicate a high receptor affinity (K D approx.400pM), with about 30,000 sites per cell occupied at saturation. Both unlabelled B-URO and m-EGF compete similarly for the binding of both 125 I-substituted derivatives. It can be concluded by physicochemical and biological criteria that B-URO and m-EGF share a common receptor site in cultured human fibroblasts.