Metallothionein is a component of exocrine pancreas secretion:
implications for zinc homeostasis.
Lisle, Robert C. De, Michael P. Sarras, Juan Hidalgo, and Glen K.
Andrews.
Departments of Anatomy and Cell Biology and Biochemistry and
Molecular Biology, University of Kansas Medical Center, Kansas City,
KS 66160 and Departamento de Biologia Celular y Fisiologia, Unidad de
Fisiologia Animal, Facultad de Ciencias, Universidad Autonoma de
Barcelona, Bellaterra 08193, Barcelona, Spain
APStracts 3:0136C, 1996.
Using transgenic mice which over-express metallothionein-I (MT-I) and
zinc-induced normal and transgenic animals, we have explored the
localization of MT in the pancreas. Light-level immunocytochemistry
demonstrated MT in acinar cells, but not islet cells. Immunolabeling
also revealed the presence of MT in pancreatic ducts, suggesting that
it is released from acinar cells. Ultrastructural immunolocalization
showed that MT was cytoplasmic, and no MT immunoreactivity was
detected in lumina of the vesicular secretory pathway. Secreted
pancreatic juice was collected from pilocarpine stimulated mice and
assayed for MT by a [109Cd]-hemoglobin-exchange assay and by RIA.
Both methods revealed high (>1000 ng/ml) levels of MT in the
stimulated secretion. The level of MT in pancreatic juice from
transgenic mice was only slightly (2-fold) increased despite dramatic
over-expression of MT-I in the pancreas (>20-fold). In contrast,
zinc-induction of MT significantly increased MT by 5-10-fold in the
pancreatic juice, in normal and transgenic mice. These data indicate
that MT is released from pancreatic acinar cells, but not by the
classical vesicular secretory pathway. In addition, MT levels in
pancreatic juice are regulated by zinc, suggesting a physiological
role of the pancreas in metal homeostasis.
Received 7 March 1996; accepted in final form 17 April 1996.
APS Manuscript Number C128-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96