Effects of Mushroom Toxins on Glycogenolysis : Comparison of Toxicity of Phalloidin, α-Amanitin and DL-Propargylglycine in Isolated Rat Hepatocytes

Abstract

The effects of phalloidin and α-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 α activity remarkably. α-Amanitin also decreased glycogen content significantly but activated phosphorylase α 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 phosphatidylinosito 4, 5-bisphosphate (PIP₂) but increased phosphoinositides breakdown. These results suggest that phalloidin alters phosphoinositides turnover and intracellular Ca²⁺ homeostasis, subsequently activates phosphorylase α, resulting in glycogenolysis in isolated rat hepatocytes.