ABSTRACT
Many of the toxins in the environment that are derived from plant and animal sources or are made by mankind affect the ion channels, ion pumps, and ion exchangers of the cell membrane and/or the membranes of the endoplasmic reticulum (ER) or sarcoplasmic reticulum (SR). Many drugs used for therapy are also toxic, especially at higher concentrations. Ion channels especially are targets for a number of different toxins and drugs. Although much of the basic data elucidating mechanisms of action have been obtained on neurons, there also are considerable data on the cardiovascular systems, e.g. heart muscle and vascular smooth muscle (VSM) cells. As a general rule (with a few notable exceptions), the actions of toxins and drugs are similar in all excitable membranes, whether they be from nerve, skeletal muscle, heart, or smooth muscle in both vertebrates and invertebrates. Because there are so many toxins, and because of space and time limitations, this chapter will focus on only some of them, particularly on some of the major cardiotoxins.
