In intact red cells diamide had no strong influence on monoester phosphate group turnover of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP) and phosphatidic acid (PA) due to the potent GSH protection of these pathways in vivo. Following the complete GSH oxidation diamide impaired the turnover of PIP and PA dramatically. However that of PIP2 did not show any change. Indeed, a drastic irreversible decrease of PIP- and PA turnover was caused by a mild oxidative stress with diamide in G6PD deficient red cells.