Human pituitary somatotropes express transforming growth factor-alpha and its receptor

Transforming growth factor-alpha (TGF-alpha) is a growth-regulatory peptide produced by a variety of transformed and non-transformed cells. Among non-transformed cells, TGF-alpha has been identified in the prolactin (PRL)- and GH-secreting cells of the bovine anterior pituitary gland. In this report, we have examined the expression of TGF-alpha in human anterior pituitary glands by Western analysis and immunohistochemistry. For the Western analysis, human pituitary glands were extracted in acid/ethanol, an acetic acid-soluble fraction was ether-precipitated and dialysed, and TGF-alpha was partially purified by C18 chromatography. TGF-alpha was then identified by immunostaining of Western transfers. Anterior pituitary extracts exhibited a major band(s) migrating at 19 kDa that was immunoreactive with a monoclonal antibody directed against the mature TGF-alpha. However, no evidence of the fully processed 6 kDa TGF-alpha was observed. We next identified TGF-alpha by immunohistochemistry. Using both monoclonal and polyclonal antibodies, specific immunoreactivity was identified in a population of secretory cells in the anterior pituitary gland. Using antibodies specific for the COOH and NH3 terminals of the TGF-alpha precursor, a comparable number of TGF-alpha-positive cells were found to contain TGF-alpha precursor sequences. These results indicate that the 19 kDa form of TGF-alpha expressed in the human pituitary gland may exist as the transmembrane form. We next sought to determine which cells express TGF-alpha in a human male pituitary gland. On frontal sections, TGF-alpha-immunopositive cells were evenly distributed in a manner and number indistinguishable from GH-immunopositive cells.(ABSTRACT TRUNCATED AT 250 WORDS)