The structure and function of Golgi apparatus as revealed by rapid freezing techique.

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Observations by mamns of rapid freezing technique: The Golgi apparatus appeared as a continuous and complicated network of stack composed of several cisterns in parallel. Number of cisterns in one stack was usually 4-7 in the exocrinosytes of pancreas, and in some preparations, the electron poacity of cisternal lumen increased gradually from cis to trans side and finally became similar to those of secretory granules. However, the so-called rigid lamella showed no increased luminal density although it located in trans side. In other preparation, the cis most cistern showed characteristic morphology. It was a flat sac of constant thickness about 30nm and sometimes arranged in a small circle. The Golgi vesicles were classified into 2 kind due to their size, namely [60nm and [40nm in diameter. The former group was found in an area between rER and cis most cistern, where an homogeneous matrix of fine reticular mashwork ebbedded. The latter was usually noticed from lateral to trans side of the stack. The peripheral margin of the Golgi stack was surrounded by a row of such vesicles, which was most obvious when viewed en face.Morphological changes by agents affecting intracellular processings of secretory proteins: Primary cultured rat hepatocytes were iincubated for 0.5 and 2hrs with either 10^6M Monensin(M), 10mM Methylamine(A), 100<micrn>M Chloroquine(c), 20mM Trisaminomethane(T), or 10 ^6<micrn>g/ml Brefeldin A (B) respectively, and compared their morphological changes with the control. In each case, rpominant changes were niticed only in the Golgi apparatus. With M, A, C, and T, the Golgi apparatus enlarged and their cisterns became dilated increasingly from cis to trans side, while, with B, most of Golgi elements disappeared leaving some vesiclar and tubular structures. The findings were consistant with the biochemical data, and suggest that the structural compomemts of Golgi apparatus maintain balance by membrane recycling mechanism.