Transmembrane potential and amino acid transport in rat hepatocytes in primary monolayer 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) depolarized regenerating cell 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 x 4 min, respectively. Ouabain (1 mM) reduced the initial rate of AIB transport into regenerating cells to 2.7 +/- 0.1 nanomoles/mg protein x 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 x 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.