Insulin-like growth factor I stimulates phospholipid synthesis in renal cortical slices without production of inositol phosphate.

The effects of insulin-like growth factor I (IGF-I) on the metabolism of phospholipids in renal cortical slices were examined using either sodium [32P]orthophosphate or myo-[3H]inositol. IGF-I was found to increase the incorporation of phosphate into phospholipids about 2-3-times above control values, leading to an increase in the concentration of total phospholipid phosphorus of 20% above control value after 1 h of incubation. The increased incorporation of phosphate into phospholipids could be prevented by 10 microM cycloheximide, while with 1 microM TPA (12-O-tetradecanoylphorbol 13-acetate) it could not. Insulin was also found to increase the incorporation of phosphate into phospholipids, but only if its concentration was at least 100-times higher than that of IGF-I. When phospholipids were prelabelled, IGF-I neither decreased the level of 32P in phospholipids nor stimulated the formation of inositol phosphates. The results show that IGF-I stimulates phospholipid synthesis without production of inositol phosphates in renal cortical slices.