RAT PANCREATIC ACINI PERMEABILIZED WITH STREPTOLYSIN-O SECRETE AMYLASE AT CA-2+ CONCENTRATIONS IN THE MICROMOLAR RANGE, WHEN PROVIDED WITH ATP AND GTP-GAMMA-S

The aim of this study was to define the conditions required for exocytosis in pancreatic acini permeabilised with the bacterial toxin streptolysin O. Treatment of a suspension of acini with streptolysin O caused the release of both the cytoplasmic enzyme lactate dehydrogenase and the zymogen granule enzyme amylase. The release of amylase occurred more quickly than that of lactate dehydrogenase and was smaller in magnitude. In addition, a component of amylase release occurred only in the presence of Ca2+ (at concentrations in the micromolar range), ATP and GTPγS. We conclude that this component represents an exocytotic event, but that the release of lactate dehydrogenase occurs through toxin-generated lesions. The concentrations of Ca2+, ATP and GTPγS causing half-maximal exocytosis were 0.7 μM, 0.2 mM and 10 μM, respectively. This system should permit a study of the mechanisms underlying regulated exocytosis in this cell type. © 1990.