Transforming growth factor type alpha in normal human adult saliva

For the first time, transforming growth factor alpha (TGF- alpha ) has been detected in the saliva of healthy adults. In saliva, the concentrations of TGF- alpha and epidermal growth factor (EGF) were determined by radioimmunoassay (RIA) to be 1-6 mu g/l saliva and 0.5-2 mu g/l saliva, respectively. The salivary TGF- alpha was partially purified about 1200-fold by an ethanol extraction, Bio-Gel P-30 molecular sieve chromatography and reverse-phase high-performance liquid chromatography (HPLC). At least three forms of TGF- alpha , with molecular weights of 6 kDa or less, were detected with molecular sieve gel filtration chromatography. A major chromatography peak, which constituted 20-30% of the extract, was a 5.6 kDa human TGF- alpha (hTGF- alpha ) molecule by using RIA, radioreceptor assay (RRA), and mitogenic activity assay techniques. Reverse-phase HPLC purification further confirmed the identity of TGF- alpha . Our findings suggest, in contrast to what was earlier assumed, that TGF- alpha is present in normal adult saliva and we hypothesize that it may play a significant role in mediating proliferation and other functions of epithelial cells in the alimentary system.