The incorporation of myo-inositol into phosphatidylinositol derivatives is stimulated during hormone-induced meiotic maturation of amphibian oocytes

The incorporation of myo-3H]inositol into phosphatidylinositol and its phosphorylated derivatives was studied by microinjection of the radioactive precursor into Xenopus laevis oocytes. Induction of meiotic maturation of the oocytes by treatment with either progesterone one or insulin resulted in a significant increase in the incorporation of myo-3H]inositol into the phospholipid fraction. This increase occurred 3-6 h after hormonal treatment, a time coincident with the start of the breakdown of the nuclear envelope, and requires protein synthesis. The effect of progesterone and insulin contrasts with the effect of acetylcholine, which acts through a muscarinic receptor causing the activation of phospholipase C, since the latter effector causes an increase in myo-3H]inositol incorporation, which is more rapid and does not require protein synthesis. These results suggest that the meiotic maturation process is connected with changes in inositol metabolism in the amphibian oocyte.