[38] Volume regulation in epithelia: Experimental approaches

Publisher Summary This chapter provides a framework within which volume regulation in epithelia can be considered and focuses on the techniques applied to determine cell volume and cell water and ions, and finish by discussing some of the preparations that have been used to study the regulation of cell volume in epithelia. Cell volume can be examined directly using a wide range of microscopy techniques applied to fixed tissues, or, more recently, to living preparations. In alternative method for monitoring rapid changes, epithelial cells of the gallbladder of Necturus are loaded with tetramethylammonium by exposure of the apical surface to a high concentration of this substance in the presence of the polyene antibiotic nystatin. After a short time, the nystatin is removed and intracellular tetramethylammonium is found, using an ion-selective electrode, to be between 2 and 15 mM, and to remain unchanged for several hours. Changes in cellular volume could then be monitored by determining the changes in intracellular tetramethylammonium concentration following changes in osmolality of the mucosa bathing solution.