Abstract
Passive Ca 2+ influx independent of ATP addition to the incubation medium, took place in plasma membrane vesicles isolated from rat liver. The rate of Ca 2+ influx was found to depend on the concentration of added Ca 2+, and on the incubation temperature, and was inhibited by La 3+, Hg 2+ and by p-chloromercuribenzoate. Influx was not blocked by calcium channel blockers, or affected by a range of uncouplers. Addition of the Ca 2+ ionophore A23187 to vesicles that had taken up the ion induced a rapid efflux of Ca 2+ especially when EGTA also was added to the incubation medium. A number of divalent cations inhibited Ca 2+ influx. The vesicles could be frozen and stored overnight with little loss in activity. The kinetics of Ca 2+ influx could be related to that which occurs in the unstimulated perfused rat liver. The data suggest that the plasma membrane vesicle preparation may be useful for further studies on the basal liver cell Ca 2+ influx system in vitro.
Published Version
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