Effects of mushroom toxins on glycogenolysis; comparison of toxicity of phalloidin, alpha-amanitin and DL-propargylglycine in isolated rat hepatocytes.

The effects of phalloidin and alpha-amanitin as toxins of Amanita species and DL-propargylglycine identified from A. abrupta on the glycogenolysis in isolated rat hepatocytes were investigated. Phalloidin decreased glycogen content and activated phosphorylase a activity remarkably. alpha-Amanitin also decreased glycogen content significantly but activated phosphorylase a activity slightly. DL-Propargylglycine slightly affected glycogenolysis. Phalloidin, which most affected glycogenolysis among the three compounds mentioned above, elevated cytosolic Ca2+ concentration ([Ca2+]i) and 45Ca uptake into cells. Phalloidin depressed slightly 3H-inositol incorporation into phosphatidylinositol (PI) and remarkably phosphatidylinositol 4,5-bisphosphate (PIP2) but increased phosphoinositides breakdown. These results suggest that phalloidin alters phosphoinositides turnover and intracellular Ca2+ homeostasis, subsequently activates phosphorylase a, resulting in glycogenolysis in isolated rat hepatocytes.