Large quantities of salt and water move across epithelial cells. These cells are able to maintain a constant volume by balancing solute entry and exit. The mechanisms for epithelial cell volume regulation and fluid transport are under investigation in this laboratory. Optical and microelectrode studies have been performed on the gallbladder of Necturus as well as cultured pancreatic and renal cells. The goal of these studies is an increased understanding of the regulation of transport in epithelia.