K+ transport in isolated rat liver cells stimulated by glucagon and insulin in vitro.

Unidirectional K+ fluxes were measured in suspensions of isolated rat liver parenchymal cells incubated with 42K+ in vitro. By tracer exchange analysis fluxes in both directions were estimated to 8-9 10(-12) mol/cm2. Glucagon in concentrations above 2 x 10(-8) M increased both influx and efflux to 160% of control values. Insulin increased influx by 12-14%, whereas efflux was apparently unaffected. Using an extracellular marker 51Cr EDTA, intracellular level of some ions was estimated in isolated liver cells: K+ = 172 mmol/kg water, Na+ = 25 mmol/kg water, Cl = 53 mmol/kg water. Cellular water content: 60%. Incubation with insulin for 1 h increased the intracellular concentration of K+ 1.7 mmol/kg water. The results indicate that glucoagon increased primarily the K+-permeability of the cell membrane, while insulin stimulates active K+ transport into the cell.