Ca2+-dependent amylase secretion from slo permeabilized rat pancreatic acini requires diffusible cytosolic proteins. Padfield, Philip J., and Ninder Panesar. Department of Internal Medicine, St. Louis University Health Sciences Center, St. Louis, MO 63104.
APStracts 2:0104G, 1995.
Streptolysin O (SLO) permeabilized pancreatic acini are now frequently used to study regulated exocytosis in the exocrine pancreas. In this paper we introduce [alpha] toxin as a possible alternative permeabilization agent to SLO. Both [alpha] toxin and streptolysin O are bacterial cytolysins, but the membranes pores generated by SLO are approximately 5-10 times larger than those formed by [alpha] toxin. The Ca2+ requirements for amylase secretion from both types of permeabilized acini were identical, maximal amylase secretion being obtained at 30[mu]M Ca2+ with an EC50 of approximately 3-4[mu]M Ca2+. However, Ca2+ stimulated amylase secretion from the SLO permeabilized acini stopped after 10-15min, unlike secretion from the [alpha] toxin permeabilized cells which continued for at least 50min. The rapid cessation of secretion from the SLO treated acini reflects the rapid decline in the responsivness of the cells observed after permeabilization. This decline in Ca2+-dependent secretion appears to be due to the loss of cytosol, as addition of purifed rat brain cytosol to non-responsive SLO-permeabilized acini reconstituted regulated secretion. As [alpha] toxin permeabilized acini maintained their responsiveness, the cytosolic factors lost from the SLO permeabilized cells must be retained within the toxin treated cells. The reconstitutive activity of the brain cytosol was non-dialysable but heat and trypsin sensitive, suggesting that the factors responsible are proteins. Of the cytosols screened (brain, liver, spleen, muscle and lacrimal) only those prepared from brain or lacrimal reconstituted Ca2+-dependent amylase secretion. Thus the cytosolic factors required for Ca2+-dependent secretion in acini appear to be specifically expressed in regulated secretory tissues. 

Received 24 February 1995; accepted in final form 19 May 1995.
APS Manuscript Number G84-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.