Effects of secretory stimulation on the Golgi apparatus and GERL of rat tracheal gland cells

Changes in the morphology and phosphatase cytochemistry of the Golgi region of hepatocytes during the acute phase response to inflammation

BACKGROUND

During the acute phase response to inflammation, the Golgi apparatus of rat hepatocytes processes an increased quantity of glycoproteins, in the form of acute phase reactants.

METHODS

The compartmental organization of the hepatocyte Golgi of control and 24 hour inflamed rats was studied, using transmission electron microscopic techniques, including cytochemistry, to detect nicotinamide adenine dinucleotide phosphatase (NADPase), thiamine pyrophosphatase (TPPase), and cytidine monophosphatase (CMPase) activity.

RESULTS

In inflamed rats, individual Golgi stacks were enlarged, but retained their organization into four compartments: 1) a phosphatase negative, perforated cis-element, 2) two mid-saccules which sometimes were positive for NADPase, 3) one or occasionally two NADPase and TPPase positive trans-saccules, and 4) a tubulovesicular trans-Golgi network (TGN) which was NADPase reactive and contained a spotty TPPase reaction product. Two of these compartments were noticeably altered in response to inflammation. The two mid-saccules were consistently and uniformly dilated. The TGN was altered to the point of being difficult to recognize and had acquired CMPase reactivity. In control rats the TGN consisted of anastomosing tubules forming cage-like structures; secretory granules containing lipoprotein particles pinched off from these. In inflamed rats, most of the cage-like TGN structures had been replaced with an extensive vesicular syncytium which produced secretory granules with a granulofilamentous content.

CONCLUSIONS

In hepatocytes from inflamed rats an apparent switch had occurred in the type of secretory material processed by the Golgi apparatus. Furthermore, the inflammation-induced increase in the size of individual Golgi stacks apparently was not due to a parallel increase in size of all Golgi saccules. Rather, saccules within given Golgi compartments responded in a characteristic and specific manner to the increase in glycoprotein processing that occurs during inflammation.

Three-dimensional observation of the Golgi apparatus in rat tracheal gland during the secretory cycle

The purpose of the present work is three-dimensional clarification of the overall configuration of the Golgi apparatus in rat tracheal serous cells including the sequence of structural modification during the secretory cycle induced by pilocarpine. From the results of both transmission electron microscopy from the serial sections, and scanning electron microscopy using the osmium-DMSO-osmium method based on maceration in dilute osmium tetroxide, the overall configuration of the Golgi apparatus shows that the Golgi stacks are joined together to make an interconnected, single Golgi complex in a cell. Connections, not only between the TGN (trans Golgi network) and rough ER (endoplasmic reticulum), but also between rough ER and cis cisternae are observed. This finding offers alternative routes for movement of substances through the cellular endomembrane system. During the secretory cycle induced by pilocarpine injection, it is evidenced that the disappearance of the TGN is accompanied by rapid discharge of secretory granules and the reconstitution of the TGN is followed by reformation of secretory materials. The beginning of the reconstitution of the TGN is indicated by vesicular buds from the sacculotubular element. These results indicate that the TGN participates directly in membrane recycling and in formation of secretory granules.