Amylase release from streptolysin O-permeabilized pancreatic acinar cells. Effects of Ca2+, guanosine 5'-[gamma-thio]triphosphate, cyclic AMP, tetanus toxin and botulinum A toxin

The molecular requirements for amylase release and the
intracellular effects of botulinum A toxin and tetanus toxin on
amylase release were investigated using rat pancreatic acinar cells
permeabilized with streptolysin O. Micromolar concentrations of
free Ca2+ evoked amylase release from these cells. Maximal release
was observed in the presence of 30 microM free Ca2+.
Ca(2+)-stimulated, but not basal, amylase release was enhanced by
guanosine 5'-[gamma-thio]triphosphate (GTP[S]) (3-4 fold) or cyclic
AMP (1.5-2 fold). Neither the two-chain forms of botulinum A toxin
and tetanus toxin, under reducing conditions, nor the light chains
of tetanus toxin, inhibited amylase release triggered by Ca2+, or
combinations of Ca2+ + GTP[S] or Ca2+ + cAMP. The lack of
inhibition was not due to inactivation of botulinum A toxin or
tetanus toxin by pancreatic acinar cell proteolytic enzymes, as
toxins previously incubated with permeabilized pancreatic acinar
cells inhibited Ca(2+)-stimulated [3H]noradrenaline release from
streptolysin O-permeabilized adrenal chromaffin cells. These data
imply that clostridial neurotoxins inhibit a Ca(2+)-dependent
mechanism which promotes exocytosis in neural and endocrine cells,
but not in exocrine cells.