Interactions of intracellular mediators of amylase secretion in permeabilized pancreatic acini.
Mouse pancreatic acini were permeabilized with streptolysin O to investigate amylase secretion stimulated by various intracellular mediators and the kinetics of secretion as a function of temperature. Amylase secretion was temperature dependent in that the initial rate of Ca2(+)-stimulated secretion increased with increasing temperature. In addition, there was no enhancement of Ca2(+)-stimulated secretion by GTP[gamma S] at 14 degrees C, while enhancement was maximal at 30 degrees C. GTP[gamma S]-mediated enhancement of secretion at a given temperature was mostly due to sustained secretion with a small increase in secretory rate. At 30 degrees C Ca2(+)-stimulated secretion was also enhanced by cAMP and phorbol ester (TPA) to similar extents as by GTP[gamma S]. The maximally effective concentration of cAMP was 1-10 microM in the presence of 0.1 mM isobutylmethylxanthine. The enhancements of Ca2(+)-stimulated amylase secretion by all combinations of cAMP (100 microM plus 0.1 mM isobutylmethylxanthine), TPA (1 microM), and GTP[gamma S] (30 microM) were fully additive. In Ca2(+)-free buffer, cAMP, TPA or GTP[gamma S] individually had no effect on amylase secretion. Together, TPA and GTP[gamma S] stimulated Ca2(+)-independent secretion, which was 187 +/- 38% of basal. Cyclic AMP together with TPA and GTP[gamma S] in the absence of Ca2+ stimulated 329 +/- 30% of basal secretion. Ca2(+)-stimulated amylase secretion was decreased about 50% by metabolic inhibition, while the enhancement by cAMP, TPA or GTP[gamma S] was totally blocked by metabolic inhibitors. These data demonstrate that amylase secretion in the acinar cell is mediated by multiple intracellular pathways which act in parallel and probably converge at a distal step in the exocytotic process.
Kitagawa
M
M
Department of Physiology, University of Michigan, Ann Arbor.
Williams
J A
JA
De Lisle
R C
RC
D000255:Adenosine Triphosphate / Q000502:physiology; D000681:Amylases / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability; D000242:Cyclic AMP / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D066298:In Vitro Techniques; D051379:Mice; D010179:Pancreas / Q000378:metabolism*; D012636:Secretory Rate / Q000187:drug effects; D013301:Streptolysins / Q000494:pharmacology; D013696:Temperature; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D001426:Bacterial Proteins; D013301:Streptolysins; C025964:streptolysin O; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D000681:Amylases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium