Assembly of heteromeric connexons in guinea-pig liver en route to the Golgi apparatus, plasma membrane and gap junctions

1. A cell fraction has been isolated from guinea-pig liver and shown to be rich in Golgi apparatus by electron microscopy. The activity of UDP-d-galactose-N-acetylglucosamine galactosyltransferase was over 100-fold greater in this cell fraction than in the liver homogenate. These data support the conclusion that the fraction was enriched in Golgi apparatus. 2. The Golgi cisternae and secretory vesicles contained electron-dense particles of 10–80nm diameter. Disruption of the Golgi apparatus cell fraction released these particles, which were separated into VLD (very-low-density) and LD (low-density) species on the basis of their density. 3. The Golgi VLD particles possessed morphological, flotational, chemical and immunochemical properties which closely resembled those of the serum VLD lipoproteins from the same animals. 4. The Golgi LD particles were rich in phospholipid, containing 48.1% by weight. The chemical composition of these particles was quite distinct from that of the serum LD lipoproteins, but did, however, show some similarity to that of the serum VLD lipoproteins. A marked resemblance was noted in the chemical characteristics of the Golgi LD and VLD particles (with the exception of triglyceride content). In addition, these two species of Golgi particles possessed the same antigenic determinant. 5. The results suggest that the Golgi VLD particles are the precursors of the serum VLD lipoproteins. On the basis of similarities in gross chemical composition and in the antigenic determinant of the Golgi LD and VLD particles, we conclude that the LD particles are probably the precursors of the VLD particles. In view of the marked differences in gross chemical composition of the Golgi LD particles and serum LD lipoproteins, it appears unlikely that the LD particles are directly secreted into the serum pool.

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The effect of a lipid-rich diet on the properties and composition of lipoprotein particles from the Golgi apparatus of guinea-pig liver

Biochemical Journal ◽

10.1042/bj1310177 ◽

1973 ◽

Vol 131 (2) ◽

pp. 177-185 ◽

Cited By ~ 28

Author(s):

M. J. Chapman ◽

G. L. Mills ◽

C. E. Taylaur

Keyword(s):

Chemical Composition ◽

Golgi Apparatus ◽

Guinea Pig ◽

Cholesteryl Ester ◽

Electron Density ◽

Guinea Pigs ◽

Cell Fraction ◽

Low Density ◽

Pig Liver ◽

Guinea Pig Liver

1. A cell fraction rich in Golgi apparatus was isolated from the livers of guinea pigs fed on a lipid-rich diet (1.6% cholesterol, 15% corn oil). 2. The Golgi cisternae and secretory vesicles contained electron-dense particles which were tentatively identified as VLD (very-low-density) and LD (low-density) lipoproteins. Particles of moderate electron density, 150–500nm in diameter, were seen associated with membranous elements of the Golgi-apparatus cell fraction. Disruption of this cell fraction permitted the release of these three species of particles, which were separated into particulate lipid, and VLD and LD lipoproteins. 3. The large particles of moderate electron density, isolated as particulate lipid, were distinct from both species of Golgi particles in their chemical composition and in possessing an immunochemically unreactive apolipoprotein(s). Morphological observations suggest that the particulate lipid arose from cytoplasmic lipid droplets which were present as contaminants of the Golgi-rich fraction. 4. The chemical and immunochemical results are consistent with the suggestion that the Golgi LD particles are precursors of the VLD particles, into which they may be transformed by the addition of both triglyceride and cholesteryl ester. The present results provide further support for the proposal that the Golgi VLD particles are precursors of the serum VLD lipoproteins in the guinea pig. 5. Hepatic Golgi VLD particles isolated from guinea pigs fed on the lipid-rich diet contained significantly higher molar amounts (relative to protein) of both cholesteryl ester and triglyceride than similar particles from animals fed on a normal diet. These results suggest that the type of Golgi VLD particle produced from the LD particle is a direct consequence of the amount and composition of the dietary lipid. 6. Hepatic Golgi LD particles isolated from guinea pigs fed on different diets were similar in chemical composition and contained approx. 50% by weight of phospholipid. We conclude that the Golgi LD particle is normally present in the Golgi-apparatus cell fraction from guinea-pig liver, and may represent the end product of lipoprotein biosynthesis in the smooth endoplasmic reticulum. 7. The serum LD lipoproteins and Golgi LD particles were quite distinct in chemical composition. However, these two lipoprotein species were immunochemically identical and exhibited a similar range of flotation rate. It appears unlikely that the Golgi LD particles are secreted as the precursors of the serum LD lipoproteins.

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Die Bedeutung der Homogenisationsart und -intensität für die Größe und Konstanz der Sauerstoffaufnahme von Meerschweinchen-Leberhomogenat / The Influence of Mode and Intensity of Homogenization on the Absolute Value and Stability of Oxygen Consumption of Guinea Pig Liver Homogenates

Zeitschrift für Naturforschung C ◽

10.1515/znc-1977-11-1205 ◽

1977 ◽

Vol 32 (11-12) ◽

pp. 908-912 ◽

Cited By ~ 5

Author(s):

H. J. Schmidt ◽

U. Schaum ◽

J. P. Pichotka

Keyword(s):

Oxygen Uptake ◽

Guinea Pig ◽

Measuring Time ◽

Pig Liver ◽

Absolute Value ◽

Modified Method ◽

Simultaneous Measurements ◽

Liver Homogenates ◽

The Absolute ◽

Guinea Pig Liver

Abstract The influence of five different methods of homogenisation (1. The method according to Potter and Elvehjem, 2. A modification of this method called Potter S, 3. The method of Dounce, 4. Homogenisation by hypersonic waves and 5. Coarce-grained homogenisation with the “Mikro-fleischwolf”) on the absolute value and stability of oxygen uptake of guinea pig liver homogenates has been investigated in simultaneous measurements. All homogenates showed a characteristic fall of oxygen uptake during measuring time (3 hours). The modified method according to Potter and Elvehjem called Potter S showed reproducible results without any influence by homogenisation intensity.

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Precision-cut Guinea-pig Liver Slices as a Tool for Studying the Toxicity of Volatile Anaesthetics

Alternatives to Laboratory Animals ◽

10.1177/026119299001800120.1 ◽

1990 ◽

Vol 18 (1_part_1) ◽

pp. 191-199

Author(s):

Hanan N. Ghantous ◽

Jeanne Fernando ◽

Scott E. Morgan ◽

A. Jay Gandolfi ◽

Klaus Brandel

Keyword(s):

Guinea Pig ◽

Rank Order ◽

Normal Liver ◽

Liver Slice ◽

Volatile Anaesthetics ◽

Pig Liver ◽

Liver Slices ◽

Guinea Pig Liver ◽

Krebs Henseleit Buffer

Cultured precision-cut liver slices retain normal liver architecture and physiological biochemical functions. Hartley male guinea-pig liver slices have proven to be a good model for studying the biotransformation and toxicity of halothane. This system was used to evaluate the biotransformation and toxicity of different volatile anaesthetics (halothane, enflurane, isoflurane and sevoflurane), and compare their effects to those of new anaesthetics (desflurane). Liver slices (250–300μm thick) were incubated in sealed roller vials, containing Krebs Henseleit buffer at 37°C under 95% O2:5% CO2 atmosphere. Volatile anaesthetics were delivered by volatilisation after pre-incubation for 1 hour to produce a constant concentration in the medium. Production of the metabolites, trifluroacetic acid and fluoride ion, was measured. Intracellular potassium ion content, protein synthesis and secretion were determined as indicators of viability of the slices. The rank order of biotransformation of anaesthetics by the liver slices was halothane >sevoflurane>isoflurane and enflurane>desflurane. The rank order of hepatotoxicity of these anaesthetics was halothane>isoflurane and enflurane>sevoflurane and desflurane. Halothane is the anaesthetic which is metabolised furthest and has the most toxic effect, while desflurane is the least metabolised anaesthetic and has the least toxicity. This in vitro cultured precision-cut liver slice system appears to be suitable for studying the biotransformation of volatile anaesthetics and correlating its role in the resulting toxicity.

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