Abstract
The role of insulin-like growth factor I (IGF-I) on the specific function of several steroidogenic cells has been recently reported. Since IGF-I is produced by several tissues, we have investigated whether bovine adrenal cells secrete this peptide. Purification of conditioned medium from adrenal cells incubated with [35S]methionine through affinity chromatography (monoclonal anti-IGF-I antibody), high pressure liquid chromatography, and polyacrylamide gel electrophoresis revealed a single band of similar Mr as pure recombinant IGF-I. Moreover, the purified adrenal-secreted IGF-I displaced bound 125I-IGF-I to its adrenal receptors, and pretreatment of adrenal cells with the purified peptide enhanced the acute corticotropin (ACTH)-induced cAMP production as recombinant IGF-I. The basal secretion of IGF-I (6 +/- 1 ng/48 h/10(6) cells) was stimulated 3-, 4.5-, and 9.5-fold by fibroblast growth factor, angiotensin II (A-II), and ACTH, respectively, but not by growth hormone. The stimulatory effects of A-II and ACTH were dose-dependent (ED50 congruent to 2.5 x 10(-8) and 1.5 x 10(-10) M, respectively), and the effects of both hormones were additive. Glucocorticoids were not the mediators of the effect of the two hormones on IGF-I secretion, since inhibition of their steroidogenic action by aminoglutethimide did not significantly modify IGF-I secretion. An immunoreactive IGF-I material was also secreted by mouse adrenal tumor cell line Y-1, but the stimulatory effect of ACTH was only 2-fold, and there was no effect of A-II. Since bovine adrenal cells contain specific IGF-I receptors and this peptide is required for the maintenance of some adrenal cell-specific function, the present data suggest that IGF-I may act in an autocrine fashion to stimulate adrenal cell differentiation stimulated by ACTH and A-II.
Highlights
[36S]methionine throughaffinitychromatographyh, igh pressure liquid chromatography, and polyacrylamide gel electrophoresisrevealeda single band of similar M, as pure recombinant insulin-like growth factor I (IGF-I)
The stimula- Using cultured bovine fasciculata cells, we have shown that tory effects of A-I1 and ACTH were dose-dependent these cells contain specificIGF type rIeceptors and thatIGF
The autoradiography of the SDS-polyacrylamide gel electrophoresis of HPLC fractions containing IGFre-vIealed a single spot corresponding to the molecular weight of IGF-I. These results indicate thatbovine fasciculata adrenalcells secrete a peptide which was recognized by monoclonal anti-IGF-I antibodies and had the samemolecular weight as thispeptide
Summary
[36S]methionine throughaffinitychromatography (monoclonalanti-IGF-I antibody)h, igh pressure liquid chromatography, and polyacrylamide gel electrophoresisrevealeda single band of similar M , as pure recombinant IGF-I. (ACTH)-induced CAMP production as recombinant several cell types are able to secrete an IGF-I-like material Reactive IGF-I material was secreted bymouse adrenal tumor cell line Y-1, but the stimulatoryeffect of ACTH was only 2-fold, and there was no effect of
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