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A peptide that is recognized by antibodies to human somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) has been partially purified from cultured Sertoli cells prepared from sexually immature rats. The mol wt of this peptide is about 25,000, as determined by gel filtration chromatography and immunoblot analysis of samples resolved by polyacrylamide gel electrophoresis. Isoelectric focusing indicated that the isoelectric point of this peptide was near neutrality. However, a smaller peptide of mol wt 8,000 that cross-reacted with antibodies to Sm-C/IGF-I, was released after gel filtration in acetic acid. Similarly, reverse phase HPLC on a C18 column under acidic conditions released a Sm-C/IGF-I immunoreactive peptide of 8,000 mol wt. This smaller species apparently resulted from the dissociation of this peptide from a binding protein. Unlike the larger neutral form, the isoelectric point of the smaller peptide was 9.8. This pI is similar to the GH-dependent Sm-C/IGF-I peptide isolated from rat serum. The small peptide, unlike the larger form, reacted in a parallel manner to human Sm-C/IGF-I in the Sm-C/IGF-I RIA and radioreceptor assays. In addition, the 8,000 mol wt peptide behaved as a progression factor in the BALB/c-3T3 assay and competed with [125I]Sm-C/IGF-I for binding to the type I Sm-C/IGF-I receptor from cultured rat Sertoli cells. In summary, results of this study demonstrate that rat Sertoli cells in culture secrete a peptide that is the rat equivalent of human Sm-C/IGF-I.
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May 1978,
National Cancer Institute monograph,
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December 1984,
Canadian journal of biochemistry and cell biology = Revue canadienne de biochimie et biologie cellulaire,
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March 1985,
Circulation research,
E P Smith, and
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August 1991,
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January 1983,
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December 1987,
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August 1987,
Biochemical and biophysical research communications,
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L L Tres
February 1987,
The Journal of neuroscience : the official journal of the Society for Neuroscience,
E P Smith, and
M E Svoboda, and
J J Van Wyk, and
A L Kierszenbaum, and
L L Tres
January 2003,
Reproductive toxicology (Elmsford, N.Y.),
E P Smith, and
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A L Kierszenbaum, and
L L Tres
December 1986,
Nihon Kyosei Shika Gakkai zasshi = The journal of Japan Orthodontic Society,
