Transforming growth factor-alpha immunoreactivity in a variety of epithelial tissues.

The immunohistochemical expression of transforming growth factor-alpha (TGF alpha) has been examined in a range of normal adult epithelial tissues from both man and rat using an anti-hTGF alpha monoclonal antibody (GF10). No differences in distribution were apparent between man and rat. In the continually renewing epithelium of the gastrointestinal tract, no staining was seen within the proliferative compartments, but strong immunoexpression was noted in various differentiated populations. In the testis, the spermatogonia were unstained, but the more luminally orientated germ cells were strongly positive. In the gastrointestinal tract, at least, any mitogenic action of TGF alpha must be mediated through a relatively long paracrine loop. In contrast, the differentiated parenchyma of kidney, salivary gland and liver remained unstained apart from collecting ducts in the kidney, striated ducts in salivary glands and bile ducts in the liver. The association of TGF alpha with tubule formation was reinforced by the very strong staining of newly forming bile ducts in a model of liver oval cell proliferation. Thus, in all the epithelia studied there was a distinct spatial pattern of TGF alpha immunoreactivity.