Freeze-fracture of drug-induced autophagocytosis in the mouse exocrine pancreas
Réz, G.; Meldolesi, J.
Laboratory Investigation; a Journal of Technical Methods and Pathology 43(3): 269-277
1980
ISSN/ISBN: 0023-6837 PMID: 7401637 Document Number: 162196
Freeze-fracture was used to investigate membrane structure in autophagic vacuoles induced in mouse pancreatic acinar cells by injection of neutral red or vinblastine. Early autophagic vacuoles (studied 20-60 min after drug injection) characterized by the presence of 2 limiting multilamellar structures. Late vacuoles (studied 4-8 h after drug injection) were identified primarily by their large size and highly irregular shape. The 2 limiting membranes of autophagic vacuoles, although originating from a common source (the limiting cisternae), were found by freeze-fracture to be distinctly different. The outer membrane always exhibited intramembrane particles on its fracture faces even though, compared to the membranes of other organelles (endoplasmic reticulum, Golgi complex and mitochondria), the density (number per unit of area) of these particles was much lower, especially in early vacuoles and the distribution more heterogeneous. Endoplasmic reticulum or Golgi membranes are probably not the direct source of the autophagic vacuole limiting cisterna, unless a partial loss of particles occurs in these membranes concomitantly with vacuole formation. The inner limiting membrane, as well as the membranes of the segragated organelles, were nearly always totally free of intramembrane particles. This was true even at early time points of the experiment, when in thin sections the trilaminar structure of these membranes was still recognizable. The loss of intramembrane particles seems to be a very early and rapid event in the process of membrane deterioration occurring inside autophagic vacuoles.