Characterization of insulin-like growth factor I and insulin receptors on cultured bovine adrenal fasciculata cells. Role of these peptides on adrenal cell function.
We have characterized insulin-like growth factor I (IGF-I) and insulin receptors in cultured bovine adrenal cells by binding and cross-linking affinity experiments. At equilibrium the dissociation constant and the number of binding sites per cell for IGF-I were 1.4 +/- (SE) 0.3 x 10(-9) M and 19,200 +/- 2,100, respectively. Under reduction conditions, disuccinimidyl suberate cross-linked [125I]iodo-IGF-I to one receptor complex with an Mr of 125,000. Adrenal cells also contain specific insulin receptors with an apparent dissociation constant (Kd) of 10(-9) M. Under reduction conditions [125I]iodo-insulin binds to one band with an approximate Mr of 125,000. IGF-I and insulin at micromolar concentrations, but not at nanomolar concentrations, slightly stimulated DNA synthesis, but markedly potentiated the mitogenic action of fibroblast growth factor. Adrenal cells cultured in a serum-free medium containing transferrin, ascorbic acid, and insulin (5 micrograms/ml) maintained fairly constant angiotensin-II (A-II) receptor concentration per cell and increased cAMP release on response to ACTH and their steroidogenic response to both ACTH and A-II. When the cells were cultured in the same medium without insulin, the number of A-II receptors significantly decreased to 65% and the increased responsiveness was blunted. Treatment of such cells for 3 days with increasing concentrations of IGF-I (1-100 ng/ml) produced a 2- to 3-fold increase in A-II receptors and enhanced the cAMP response (3- to 4-fold) to ACTH and the steroidogenic response (4- to 6-fold) to ACTH and A-II. These effects were time and dose dependent (ED50 approximately equal to 10(-9) M). Insulin at micromolar concentrations produced an effect similar to that of IGF-I, but at nanomolar concentrations the effect was far less. The enhanced steroidogenic responsiveness of IGF-I and insulin-treated cells were related to an enhanced capacity to produce pregnenolone and an increased activity of several steroid hydroxylases. These results indicate that both IGF-I and insulin, acting through their own receptor, play an important role in the maintenance of specific adrenal cell functions. However, at physiological concentrations IGF-I is more potent than insulin.
Penhoat
A
A
INSERM U 307, Hôpital Debrousse, Lyon, France.
Chatelain
P G
PG
Jaillard
C
C
Saez
J M
JM
D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D003345:Corticosterone / Q000096:biosynthesis; D003432:Cross-Linking Reagents; D000242:Cyclic AMP / Q000096:biosynthesis; D004247:DNA / Q000096:biosynthesis; D007328:Insulin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D007457:Iodine Radioisotopes / Q000378:metabolism; D011284:Pregnenolone / Q000096:biosynthesis; D011972:Receptor, Insulin / Q000378:metabolism*; D011945:Receptors, Angiotensin / Q000187:drug effects / Q000378:metabolism; D017451:Receptors, Somatomedin
D003432:Cross-Linking Reagents; D007328:Insulin; D007457:Iodine Radioisotopes; D011945:Receptors, Angiotensin; D017451:Receptors, Somatomedin; C008147:insulin, iodo-; D000804:Angiotensin II; D007334:Insulin-Like Growth Factor I; D011284:Pregnenolone; D000324:Adrenocorticotropic Hormone; D004247:DNA; D000242:Cyclic AMP; D011972:Receptor, Insulin; D003345:Corticosterone