The identification of urogastrone in serum, saliva, and gastric juice.

Urogastrone, a peptide isolated from human urine, is known to cause inhibition of gastric acid secretion and proliferation of fibroblasts in culture; furthermore immunofluorescent localization techniques show it to be present in submandibular and Brunner's glands. Serum, saliva, and gastric juice samples have now been fractionated upon Sephadex G-200 and G-50 and the immunoreactive urogastrone located using a specific radioimmunoassay. Biologic activity was shown by mitogenic studies with 3T6 fibroblasts. In serum, the major immunoreactive component was ca. 1-2 X 10(5) daltons, but trypsin treatment then gave a smaller biologically active species in the same position as pure urogastrone on Sephadex G-50. Both saliva and gastric juice showed major components at the position defined by urogastrone, and these also stimulated the uptake of [H]thymidine into the fibroblasts. It is concluded that a urogastrone-like molecule can be released enzymically from a high molecular weight serum precursor and that the small biologically active peptide is also a normal component of saliva and gastric juice.