| Abstract: |
Previous investigations suggested that resistance to GH was the cause of short stature of African Pygmies. Because many of the actions of GH are mediated by insulin-like growth factor I (IGF-I), we sought to determine whether Pygmy tissue was responsive to IGF-I. An initial effort to obtain HTLV-II-transformed T lymphoblast cell lines resulted in a single cell line that showed complete resistance to both IGF-I and GH in a clonal proliferation assay as well as decreased IGF-I binding. In the current study, we examined T cell lines from seven Efe Pygmy subjects, three neighboring Lese farmers, and six American controls and quantified clonal responses to IGF-I, GH, and insulin. The T cell lines from the Efe Pygmies were all completely resistant to the growth-promoting actions of IGF-I concentrations less than 250 μg/L and GH concentrations less than 500 μg/L. The Lese population, with whom there is admixture with the Efe population, showed heights and clonal responses to IGF-I and GH intermediate between those of Pygmies and American controls. The Pygmy T cell lines showed reduced clonal proliferation in response to high insulin concentrations known to act through the IGF-I receptor. These findings indicate that genetic IGF-I resistance is present in the T cell lines of Efe Pygmies and suggest that unresponsiveness to IGF-I may be responsible for their short stature. © 1995 by The Endocrine Society. |
