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Compartmentalization of pancreatic secretory zymogen granules as revealed by low-voltage transmission electron microscopy.

The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society (2011-08-13)
Moise Bendayan, Irene Londono, Eugene Paransky
ABSTRACT

Low-voltage (5-kV) transmission electron microscopy revealed a novel aspect of the pancreatic acinar cell secretory granules not previously detected by conventional (80-kV) transmission electron microscopy. Examination of ultra-thin (30-nm) sections of non-osmicated, stain-free pancreatic tissue sections by low-voltage electron microscopy revealed the existence of granules with non-homogeneous matrix and sub-compartments having circular or oval profiles of different electron densities and sizes. Such partition is completely masked when observing tissues after postfixation with osmium tetroxide by low-voltage transmission electron microscopy at 5 kV and/or when thicker sections (70 nm) are examined at 80 kV. This morphological partition reflects an internal compartmentalization of the granule content that was previously predicted by morphological, physiological, and biochemical means. It corresponds to the segregation of the different secretory proteins inside the granule as demonstrated by high-resolution immunocytochemistry and reflects a well-organized aggregation of the secretory proteins at the time of granule formation in the trans-Golgi. Such partition of the granule matrix undergoes changes under experimental conditions known to alter the secretory process such as stimulation of secretion or diabetes.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Os EnCat® 40, extent of labeling: 0.3 mmol/g Os loading
Sigma-Aldrich
Osmium tetroxide, Sealed ampule.
Sigma-Aldrich
Osmium tetroxide, ACS reagent, ≥98.0%
Sigma-Aldrich
Osmium tetroxide, ReagentPlus®, 99.8%
Sigma-Aldrich
Osmium tetroxide solution, suitable for electron microscopy, 4% in H2O
Sigma-Aldrich
Osmium tetroxide solution, suitable for electron microscopy, 2% in H2O
Sigma-Aldrich
Osmium tetroxide solution, 4 wt. % in H2O
Sigma-Aldrich
Osmium tetroxide solution, 2.5 wt. % in tert-butanol