[The effect of calcium antagonists on intracellular transport of epidermal growth factor and the conjugate of epidermal growth factor with pseudomonas exotoxin].

Calcium antagonists, verapamil and D600, enhance the toxicity of EGF-PE and anti-TFR-PE. EGF and EGF-PE are accumulated in their intact form in the lysosomes of cells treated with D600 or verapamil. Verapamil and D600 decrease the activity of lysosomal enzymes, especially of cathepsin B. Verapamil may enhance the cytotoxicity of EGF-PE by blocking lysosomal degradation of EGF-PE.