ABSORPTION OF EPIDERMAL GROWTH-FACTOR OCCURS THROUGH THE GASTROINTESTINAL-TRACT AND ORAL CAVITY IN ADULT-RATS

Introduction of radiolabeled epidermal growth factor (I-125-EGF) by ga vage or sublingual confinement resulted in a time-dependent uptake and systemic organ dissemination in the adult rat. Intact EGF was recover ed primarily from the tongue, parotid, and sublingual/submandibular gl ands after administration by sublingual lozenge, whereas gastrointesti nal administration resulted in I-125-EGF recovery primarily from plasm a, stomach, and lung. Recovered radiolabeled EGF retained the ability to bind to the EGF receptor. Sialoadenectomy caused an increase in I-1 25-EGF in most tissues by both routes of administration. Thus, in the adult rat, at least two pathways exist for the uptake and distribution for salivary gland-derived EGF present in saliva. With further analys es, sublingual absorbance of EGF may therefore provide a potential del ivery route for therapeutic use of growth factor, which avoids the hep atic destruction of EGF after oral administration.