Transmembrane Potential and Amino Acid Transport in Rat Hepatocytes in Primary Monolaver Culture

Transmembrane potential (Em) and alpha‐aminoisobutyric acid (AIB) transport were measured in primary monolayer cultures of rat hepatocytes obtained from unoperated control rats and from rats 12 hr following partial hepatectomy. Measurements were performed 20–24 hr after plating the cells. The capacity of both kinds of cells to concentrate AIB depended upon extracellular sodium; however, the steady‐state accumulation in regenerating cells was twice that of control cells. Transmembrane potentials, recorded with glass microelectrodes, were –13 ± 0.6 mV and –27 ± 1.6 mV in control and regenerating cells, respectively. Ouabain (1 mM) depolarlized regenerating cells to –18 ± 1.0 mV, but it had no effect on control cells. The initial rates of 1 mM AIB transport into control and regenerating cells were 1.2 ± 0.1 and 3.1 ± 0.1 nanomoles/mg protein × 4 min, respectively. Ouabain (1 mM) reduced the initial rate of AIB transport into regenerating cells to 2.7 ± 0.1 nanomoles/mg protein × 4 min, but it had no effect on AIB transport into control cells. Glucagon (10−7 M) added to control cells 12 hr before measurements hyperpolarized Em to –31 ± 1.3 mV and increased AIB transport rate to 3.1 nanomoles/mg protein × 4 min. The results suggest a relationship between increases in Em and increases in AIB transport in rat hepatocytes. An electrogenic Na‐K pump may be involved in both of these events