[Ionic-channel diseases]

This review illustrates several hereditary diseases caused by mutations in genes which encode various ion channels activated by voltage or neurotransmitters. Many physiological processes depend upon the proper functioning of plasma membrane ion channels and this is most apparent in absorptive and secretory epithelia, and in electrically excitable tissues such as nerve and muscle. By combining the information from electrophysiological recordings with molecular biological techniques, further insight can be gained into the gene expression and protein structure of ionic channels. This combination has resulted in a structure-function analysis revealing the molecular substructures of the ionic channels responsible for the processes of permeation and selectivity of activation and inactivation and different types of block. Using molecular biologic tools, these abnormal channels can be identified and their molecular defects defined. Advances in these areas now provide the basis for a rational approach to the classification and treatment of these disorders of membrane excitation.