Laboratory  of  John G. Forte

Department of Cell & Molecular Biology,  University of California, Berkeley
 
 

"Tubulovesicles" (or "tubulocisternae") —
cytoplasmic pool of parietal cell membranes that contain the H,K-ATPase ("proton pump") and that can fuse with the apical (canalicular) membrane upon stimulation

 
TEM of resting parietal cell from piglet stomach, showing canaliculus (C) surrounded by numerous tubulovesicles (TV) and mitochondria.  Bar = 1μm TEM of maximally stimulated parietal cell (piglet), showing greatly enlarged canaliculi with elongated microvilli.  Remaining space has densely packed mitochondria and very few tubulovesicles.  Bar = 1μm

From:

 
  HANDBOOK OF PHYSIOLOGY — THE GASTROINTESTINAL SYSTEM III,   1989
 

Chapter 11:  Cell biology of hydrochloric acid secretion
  John G. Forte  and  Andrew Soll  

 

 

 

 

  Recently, high-pressure freezing was used to obtain better preservation of fine subcellular morphology.  When serial thin sections were then used to reconstruct 3-dimensional shapes of the small membranous structures long called "tubulovesicles," the vesicles were seen to occur mostly as stacks of flattened cisternae.  The term, "tubulocisternae," was coined to designate these structures, but long familiarity favors continued reference to "tubulovesicles."  These 3-dimensional reconstructions add support for the view that the membranes containing most of the H,K-ATPase in the resting cell are not continuous with the canalicular membrane, but must join with the latter by a process of membrane fusion when the cell is stimulated.  
 
 



From Duman, et al., J Cell Sci. 2002:



A.   3-D reconstruction of "tubulocisternae" in rabbit parietal cells, from serial thin sections after high-pressure freezing and freeze-substitution.  Each membrane-bounded structure determined to have no membrane continuity with a neighboring structure was given a distinct color.  Crude outlines of mitochondria are included.  Bar = 0.5μm








B.   Lower-resolution 3-D reconstruction of a region of tubulocisternae surrounding part of a canaliculus (cut-away blue sheet structure).  Bar = 1μm





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