Isolated rat hepatocyte couplets: a primary secretory unit for electrophysiologic studies of bile secretory function.

Abstract

Hepatocyte couplets were isolated by collagenase perfusion from rat liver. Between adjacent cells, the bile canaliculus forms a closed space into which secretion occurs. As in intact liver, Mg2+-ATPase is localized at the canalicular lumen, the organic anion fluorescein is excreted, and secretion is modified by osmotic gradients. By passing a microelectrode through one cell into the canalicular vacuole, a transepithelial potential profile was obtained. In 27 cell couplets the steady-state intracellular (-26.3 .+-. 5.3 mV) and intracanalicular (-5.9 .+-. 3.3 mV) potentials were recorded at 37.degree. C with reference to the external medium. Input resistances were determined within the cell (86 .+-. 23 M.OMEGA.) and in the bile canalicular lumen (32 .+-. 17 M.OMEGA.) by passing current pulses through the microelectrode. The data define electrical driving forces for ion transport across the sinusoidal, canalicular and paracellular barriers and indicate ion permeation across a leaky paracellular junctional pathway. The isolated hepatocyte couplet may be an effective model for electrophysiologic studies of bile secretory function.