Electrophysiology of Ion Transport in Teleost Intestinal Cells

This chapter describes the electrophysiology of ion transport in teleost intestinal cells. The teleost intestine performs several functions, including the absorptive transport of nutrients essential for metabolism and growth and the active transport of salts and water as a part of hydromineral homeostasis. The absorption of dietary Na⁺ and Cl⁻ from the intestinal lumen in freshwater fishes replaces salt lost by diffusion to the dilute external medium, whereas in seawater fishes, salt absorption from the intestine following the ingestion of seawater drives the absorption of water to replace the loss to the hyperosmotic external environment. The thermodynamic feasibility of passive transmembrane movement in vivo under actual physiological conditions will depend on the composition of the intestinal fluid. Electrophysiological studies of individual dissociated enterocytes using the whole-cell voltage clamp technique removes the complications of paracellular conductances and of gap junction-mediated lateral current spread inherent in the studies of cells in the intact epithelium.