Activation of calcium channels by Maitotoxin

Publisher Summary This chapter describes three techniques that enhance the understanding of the action of maitotoxin by using 45 Ca 2+ to monitor calcium ion flux. The techniques are not new but are adapted for use with viable dispersed anterior pituitary cells in suspension. Methodology for monitoring 45 Ca 2+ uptake, fractional 45 Ca 2+ efflux, and net 45 Ca 2+ efflux are described with reference to the effects of maitotoxin on these processes. Maitotoxin is a water-soluble material extracted from a marine dinoflagellate and bears the Tahitian name for a species of surgeonfish in which it was also recognized. Maitotoxin is not yet characterized but is extremely lethal when injected into mice; it stimulates a wide variety of physiological processes, all sharing the apparent property of being dependent on extracellular calcium. The spectrum of its activity and the apparent lack of ionophoretic properties suggest that maitotoxin activates calcium channels to exert its biological actions.