Fine Structural Changes in Response to Hormonal Stimulation of the Perfused Canine Pancreas

Abstract

The dog pancreas isolated in situ was perfused with oxygenated dog blood and stimulated with pancreozymin, sccretin, or both. There were no significant changes in the fine structure of the acinar, centroacinar, or duct cells attributable to the perfusion. Combined glutaraldehyde and osmium fixation gave good preservation of the secretory products of the acinar cell. Before stimulation, the lumen of the acini is filled with material similar in texture to the content of the zymogen granules, but of somewhat lower density. Release of secretion commonly takes place by coalescence of the limiting membrane of zymogen granules with the plasmalemma, but one granule opening at the surface may frequently be joined by others coalescing with its membrane and forming an interconnected series all with contents having the same texture as the released zymogen. Such a mechanism seems to permit a more rapid release of secretory product than discharge of individual granules. Pancreozymin stimulation caused marked depletion of zymogen granules, but no obvious changes in the Golgi apparatus. It is clear, therefore, that this hormone exerts its effect upon release of granules rather than upon their formation. Sccretin stimulation of water and bicarbonate secretion caused a marked washing out of the luminal contents, but had little detectable effect on cellular structure.

Ca2+‐induced fusion of golgi‐derived secretory vesicles isolated from rat liver

“…This type of intracellular transfer is well established for various secretory cells and may be adopted also for the hepatocyte. Recent investigations have shown that secretory vesicles fuse with each other during secretion in mast cells [4] exocrine [5,6] and endocrine pancreatic tissue [7] . The intervesicular fusion provides a tool for studies on membrane fusion, since Colgi-derived vesicles can be isolated from the hepatocyte and their interaction with various agents, suggested to trigger membrane fusion, can be monitored by freeze-cleaving.…”

Dynamic Changes in the Ultrastructure of the Acinar Cell of the Rat Parotid Gland During the Secretory Cycle

“…11) . Although they seemed to be more abundant [2][3][4][5][6] hr after the onset of secretion (Fig . 9), their occurrence is as yet not clearly correlated with the secretory cycle .…”

Fusion of secretory vesicles isolated from rat liver

“…Exocytosis requires the fusion of the vesicle membrane with the plasma membrane. However, as already shown in several cells, the stimulus for secretion not only induces the fusion of the plasma membrane with the vesicular membrane but also of secretory vesicles among themselves [2,3,6,18,29,39,53,65]. Thus the exocytotic process appears to involve both types of fusions.…”

“…8a). The twinned structure of completely fused vesicles does not differ from that found in stimulated secretory cells [2,3,6,12,18,29,39,53,65]. Magnification of Fig.…”

“…Intervesicular fusion of secretory vesicles, as well as the interaction between the cell membrane and the vesicle membrane, was observed in a variety of secretory cells [2,3,6,18,29,39,53,65]. Douglas [20] showed that in "compound exocytosis" by mast cells an external stimulus initiates fusion between secretory vesicle membranes and the 0022-2631/78/0040-0343 $4.40 9 Springer-Verlag New York Inc.…”