Identification and characterization of insulin-like growth factor I (IGF-I) and IGF-II/mannose-6-phosphate (IGF-II/M6P) receptors in bovine adrenal cells.
We have identified and characterized insulin-like growth factor I (IGF-I) and IGF-II/mannose-6-phosphate (IGF-II/M6P) receptors in bovine adrenal cells. Iodine-125-labeled IGF-I ([125I]IGF-I) binding was characteristic of the IGF-I receptor, and binding kinetics as well as receptor densities were similar in cortical and medullary membranes. Scatchard analysis of [125I]IGF-I binding to cultured adrenocortical cells showed a single class of high-affinity binding sites with a Kd of 1.4 nmol/l and an average of 150,000 binding sites/cell. Affinity cross-linking experiments displayed a band at an apparent molecular weight of 135 kD, corresponding to the size of the alpha-subunit of the IGF-I receptor. In analogy, the binding of [125I]IGF-II to bovine adrenal membranes was characteristic of the IGF-II/M6P receptor and no differences between cortical and medullary membrane fractions were found. Scatchard analysis revealed a single class of high-affinity binding sites in adrenocortical cells with a Kd of 1.1 nmol/l and an average of 280,000 binding sites/cell. The identity of the IGF-II/M6P receptor was confirmed by western blotting of adrenocortical membranes with an anti-IGF-II/M6P receptor antibody and by affinity cross-linking of adrenocortical cells with labeled IGF-II. In conclusion, we have identified and characterized IGF-I and IGF-II/M6P receptors in bovine adrenocortical as well as medullary cells. In both regions of the bovine adrenal gland the IGF-II/M6P receptor is much more abundant than the IGF-I receptor.
Weber
M M
MM
Medical Department II, University of Munich, Germany.
Kiess
W
W
Beikler
T
T
Simmler
P
P
Reichel
M
M
Adelmann
B
B
Kessler
U
U
Engelhardt
D
D
D000302:Adrenal Cortex / Q000737:chemistry* / Q000166:cytology* / Q000648:ultrastructure; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002417:Cattle; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D002478:Cells, Cultured; D011485:Protein Binding; D017526:Receptor, IGF Type 1 / Q000032:analysis*; D017527:Receptor, IGF Type 2 / Q000032:analysis*
D017527:Receptor, IGF Type 2; D017526:Receptor, IGF Type 1