Pancreatic acinar cells: effects of lanthanum ions on amylase release and calcium ion fluxes

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Abstract
1. The effect of La(3+) on amylase release and Ca(2+) fluxes in mouse pancreatic fragments in vitro was studied.2. Amylase release was increased by 0.1 mM-La(3+) and progressively inhibited by 1.0-10 mM-La(3+). Non-stimulated and bethanecol stimulated secretion were altered in an identical manner. Inhibition of amylase release was rapid and reversible.3. Uptake of (45)Ca(2+) was multiphasic with equilibrium with stable Ca(2+) still not complete after 2 hr. La(3+) (10 mM) limited uptake of (45)Ca(2+) to the extracellular space and slightly decreased total Ca(2+) content. Lower concentrations of La(3+) affected (45)Ca(2+) uptake and total Ca(2+) content in a biphasic manner which paralleled effects on amylase release.4. La(3+) restricted washout of (45)Ca(2+) to isotope in the extracellular space and abolished the bethanecol-stimulated increase in (45)Ca(2+) efflux.5. Uptake of (45)Ca(2+) into intracellular space, as measured by the ;lanthanum' method, was not affected by bethanecol.6. Tissue ultrastructure and Na(+) and K(+) content were not affected by La(3+).7. It is concluded that an influx of extracellular Ca(2+) is not important for triggering of secretion and that La(3+) may inhibit amylase release by acting on the release process rather than on Ca(2+) influx.