A significant increase of lysophosphatidylinositol 4‐phosphate with insulin in isolated rat fat cells

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Abstract
We studied the effects of insulin on the incorporation of 32Pi into phospholipids in rat fat cells. When the cells were treated with insulin, a new radioactive phospholipid was detected on thin layer chromatography. The substance migrated slower than phosphatidylinositol 4,5‐bisphosphate and was hardly detectable in the absence of insulin. This effect of insulin was both time‐ and dose‐dependent with half‐maximal stimulation at 120 μU/ml. Pretreatment of insulin with anti‐insulin antibody or the cells with anti‐insulin receptor anti‐body inhibited the effect of insulin. The product of phosphatidylinositol 4‐phosphate hydrolysed by phospholipase A2 was coincided with the substance on thin layer chromatography. Quinacrine inhibited the formation of the substance in a dose‐dependent manner. These results suggested that insulin stimulates the generation of lysophosphatidylinositol 4‐phosphate through the insulin‐receptor interaction.