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Transforming growth factor- (TGF-) is a growth-regulatory peptide produced by a variety of transformed and non-transformed cells. Among non-transformed cells, TGF- 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- 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- was partially purified by C18 chromatography. TGF- 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-. However, no evidence of the fully processed 6 kDa TGF- was observed.

We next identified TGF- 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- precursor, a comparable number of TGF--positive cells were found to contain TGF- precursor sequences. These results indicate that the 19 kDa form of TGF- expressed in the human pituitary gland may exist as the transmembrane form.

We next sought to determine which cells express TGF- in a human male pituitary gland. On frontal sections, TGF--immunopositive cells were evenly distributed in a manner and number indistinguishable from GH-immunopositive cells. By contrast, PRL-immunopositive cells in midfrontal sections were largely restricted to the lateral wings and extended dorsally to the neural lobe. TGF- was positively co-localized to GH-immunopositive cells but not in PRL-immunopositive cells by immunostaining of consecutive sections. TGF--immunopositive cells were also immunopositive for the epidermal growth factor receptor, indicating that TGF- has the capacity for autocrine action in the human pituitary gland.

These results indicate that TGF- is expressed in the human anterior pituitary gland and it is not proteolytically processed into the mature 6 kDa form. In addition, immunohistochemistry of an adult male human pituitary gland indicates that TGF- is expressed in somatotropes and has the capacity for autocrine action.

Journal of Endocrinology (1994) 141, 547–554

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