Turtle Colon: Keeping Track of Transporters in the Apical and Basolateral Membranes

This chapter describes the attempts to identify and characterize the individual transporters that comprise the molecular basis for the ion transport properties of the turtle colon. One of the vexing problems associated with epithelial cells is their tendency to lose their highly differentiated properties when they are isolated from one another. Therefore, to obtain information about individual apical and basolateral transporters, it has been necessary to design experimental strategies that permit some degree of functional isolation of the transporters of interest while preserving the structural integrity of the cell layer. In several instances the turtle colon has proved to be uniquely suited to this type of experimental approach. Depending on the prevailing osmotic conditions at least three additional transport elements might be present in the basolateral membranes. Cell swelling is associated with the activation of a specific basolateral conductance that is blocked by quinidine or lidocaine