studies in which the Trp388 and Trp412 in TM10 and TM11 of the purified protein are labeled upon exposure to labeled cytochalasin B. Since mutating Trp388 and Trp412 does not completely reduce inhibition of GLUT1, it is assumed that other sites are involved in CB binding as well. Therapeutic uses For therapeutic purposes, research on cytochalasin B is done. In order to do so, the effects of cytochalasin B on tumor cells by BCG (Bacillus Calmette-Guerin)-activated macrophages were examined. It showed that cytochalasin B enhances tumor cell lysis and stasis due to activated macrophages at a concentration of 10−7 M. Cytochalasin B does not act on the macrophage itself, but does exert its effect predominantly on the tumor cell. A reason for this could be, that the actin filament formation, which could be important for the destruction of tumor cells by activated macrophages, is inhibited by cytochalasin B. Further effects Cytochalasin B has an effect on thyroid hormone and growth hormone secretion. Phosphatidylcholine and phosphatidylethanolamine biosynthesis is inhibited by cytochalasin B, as shown by George et al. It does so by inhibiting the conversion of phosphoethanolamine to cytidinediphosphate-ethanolamine. It was proposed that the mechanism is associated with alterations of intracellular calcium ions. Cytochalasin B also has effects on bacteria. For example, the growth and differentiation of E. histolytica is inhibited.[56] Furthermore, cytochalasin B has been shown to have an inhibitory effect on tumor cell growth without causing prolonged and/or profound immunosuppressive effects. Natural context In nature, cytochalasin B is involved in fungal virulence, food spoilage and the maintenance of the symbiosis between host and symbiont. References Merck Index 13, 2819. Actin inhibitors Lactones Mycotoxins Vinylidene compounds