Rapid changes in phospholipid metabolism in the nuclei of Swiss 3T3 cells induced by treatment of the cells with insulin-like growth factor I.

When highly-purified nuclei of Swiss-mouse 3T3 cells are incubated with [32P]-gamma ATP, radioactivity is incorporated into phosphatidic acid and the two polyphosphoinositol lipids, phosphatidylinositol(4)P and phosphatidylinositol(4,5)P2. If the cells are pre-treated with insulin-like growth factor I, this incorporation into the phospholipids is decreased. The effect is maximal by 2 minutes, is transient in that it has disappeared by one hour, and is increased markedly by the co-addition of bombesin, even though bombesin alone has no effect. We suggest that some aspect of polyphosphoinositide metabolism is altered in the nucleus (leading to a decreased radiolabelling) when the cells are treated with mitogenic growth factors, and that this change in inositide metabolism is a very early event in the sequence leading to cell division.