Insulin-like growth factor-I and insulin increase the stimulatory guanine nucleotide binding protein (Gs) in cultured bovine adrenal cells.
The present study shows that pretreatment of BAC cells with insulin or insulin-like growth factor-I (IGF-I) enhances the cAMP response to maximal concentrations of ACTH and cholera toxin. However, the effects of IGF-I at a nanomolar concentration (50 ng/ml) were higher than for insulin at the same concentration but similar for insulin at a micromolar concentration (10 micrograms/ml). We have investigated whether the effects of the two peptides can be related to some modifications of the guanine nucleotide regulatory binding protein Gs. Insulin enhanced Gs as observed by ADP ribosylation and immunoblotting but the effects were approximately the same at nanomolar and micromolar concentrations; again, the effects of IGF-I (50 ng/ml) were higher. These results indicate that both IGF-I and insulin increase the Gs complex of adenylate cyclase, but IGF-I is more potent than insulin at physiological concentrations.
Begeot
M
M
INSERM U 307, Hôpital Debrousse, Lyon, France.
Langlois
D
D
Saez
J M
JM
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000302:Adrenal Cortex / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015151:Immunoblotting; D007328:Insulin / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D013002:Somatomedins / Q000502:physiology*
D007328:Insulin; D008565:Membrane Proteins; D013002:Somatomedins; D000246:Adenosine Diphosphate Ribose; D007334:Insulin-Like Growth Factor I; D000242:Cyclic AMP; D019204:GTP-Binding Proteins