Quantitative Determination of Myoinositol, Inositol 1‐Phosphate, Inositol Cyclic 1 : 2‐Phosphate and Glycerylphosphoinositol in Normal and Rous‐Sarcoma‐Virus‐Transformed Quail Fibroblasts under Different Growth Conditions

Myoinositol and its phosphorylated derivatives have been quantitatively determined in normal and Rous‐sarcoma‐virus‐transformed quail cells under various growth conditions using [2‐ 3 H]‐myoinositol at isotope equilibrium conditions. The following amounts were determined (nmol/μmol phospholipid, as a unit of cell mass): exponentially growing normal and tumor cells contained 25–40 nmol free inositol, 0.40–0.45 nmol myoinositol 1‐phosphate, 0.30–0.50 nmol glyceryl‐phosphoinositol, and 0.03–0.04 nmol myoinositol cyclic 1 : 2‐phosphate. At high cell populations in the absence of serum, conditions which result in cessation of growth by normal but not by tumor cells, changed levels were found for glycerylphosphoinositol and free inositol. In tumor cells the levels of these two compounds increased to 0.64 nmol and 64 nmol, respectively. In normal cells glycerylphosphoinositol increased to 0.95 nmol and free inositol showed highly elevated levels of 144 nmol. At short pulses the specific activities of inositol 1‐phosphate and inositol cyclic 1 : 2‐phosphate were found to be higher than that of phosphatidylinositol. This was not the case for glycerylphosphoinositol.