Biogenesis of Smooth Endoplasmic Reticulum in Hepatocytes of Phenobarbital Treated Rats

1974 ◽  
Vol 32 ◽  
pp. 308-309
Author(s):  
Joan A. Higgins
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Membrane Formation ◽  
Drug Detoxification ◽  
Marked Proliferation

In response to intraperitoneal injections of phenobarbital there is a marked proliferation of smooth endoplasmic reticulum membranes (s.e.r.) of rat hepatocytes, with little change in other membranous organelles. This increased membrane formation is accompanied by a rise in the specific activity of the enzymes involved in drug detoxification initially in the rough endoplasmic reticulum (r.e.r.) followed by a rise in the s.e.r. There is also an increased accumulation of glycerophospholipid in the newly formed s.e.r.

scholarly journals DIFFERENTIATION OF ENDOPLASMIC RETICULUM IN HEPATOCYTES

1971 ◽  
Vol 49 (2) ◽  
pp. 264-287 ◽  
Author(s):  
A. Leskes ◽  
P. Siekevitz ◽  
G. E. Palade
Keyword(s):  
Endoplasmic Reticulum ◽  
Phosphatase Activity ◽  
Rough Endoplasmic Reticulum ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Adult Level ◽  
Enzyme Specific Activity ◽  
Cytochemical Reaction ◽  
And Control

The distribution of glucose-6-phosphatase activity in rat hepatocytes during a period of rapid endoplasmic reticulum differentiation (4 days before birth-1 day after birth) was studied by electron microscope cytochemistry. Techniques were devised to insure adequate morphological preservation, retain glucose-6-phosphatase activity, and control some other possible artifacts. At all stages examined the lead phosphate deposited by the cytochemical reaction is localized to the endoplasmic reticulum and the nuclear envelope. At 4 days before birth, when the enzyme specific activity is only a few per cent of the adult level, the lead deposit is present in only a few hepatocytes. In these cells a light deposit is seen throughout the entire rough-surfaced endoplasmic reticulum. At birth, when the specific activity of glucose-6-phosphatase is approximately equal to that of the adult, nearly all cells show a positive reaction for the enzyme and, again, the deposit is evenly distributed throughout the entire endoplasmic reticulum. By 24 hr postparturition all of the rough endoplasmic reticulum, and in addition the newly formed smooth endoplasmic reticulum, contains heavy lead deposits; enzyme activity at this stage is 250% of the adult level. These findings indicate that glucose-6-phosphatase develops simultaneously within all of the rough endoplasmic reticulum membranes of a given cell, although asynchronously in the hepatocyte population as a whole. In addition, the enzyme appears throughout the entire smooth endoplasmic reticulum as the membranes form during the first 24 hr after birth. The results suggest a lack of differentiation within the endoplasmic reticulum with respect to the distribution of glucose-6-phosphatase at the present level of resolution.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

scholarly journals Glycosyltransferase activities in Golgi complex and endoplasmic reticulum fractions isolated from African trypanosomes.

1984 ◽  
Vol 99 (2) ◽  
pp. 569-577 ◽  
Author(s):  
D J Grab ◽  
S Ito ◽  
U A Kara ◽  
L Rovis
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Smooth Endoplasmic Reticulum ◽  
Surface Glycoprotein ◽  
Relative Distribution ◽  
African Trypanosomes ◽  
Independent Form ◽  
Variable Surface ◽  
Dependent Form

Highly enriched Golgi complex and endoplasmic reticulum fractions were isolated from total microsomes obtained from Trypanosoma brucei, Trypanosoma congolense, and Trypanosoma vivax, and tested for glycosyltransferase activity. Purity of the fractions was assessed by electron microscopy as well as by biochemical analysis. The relative distribution of all the glycosyltransferases was remarkably similar for the three species of African trypanosomes studied. The Golgi complex fraction contained most of the galactosyltransferase activity followed by the smooth and rough endoplasmic reticulum fractions. The dolichol-dependent mannosyltransferase activities were highest for the rough endoplasmic reticulum, lower for the smooth endoplasmic reticulum, and lowest for the Golgi complex. Although the dolichol-independent form of N-acetylglucosaminyltransferase was essentially similar in all the fractions, the dolichol-dependent form of this enzyme was much higher in the endoplasmic reticulum fractions than in the Golgi complex fraction. Inhibition of this latter activity in the smooth endoplasmic reticulum fraction by tunicamycin A1 suggests that core glycosylation of the variable surface glycoprotein may occur in this organelle and not in the rough endoplasmic reticulum as previously assumed.

Heterogeneity of phospholipid synthesis in rat liver endoplasmic reticulum during proliferation of smooth membranes

1976 ◽  
Vol 22 (1) ◽  
pp. 173-197
Author(s):  
J.A. Higgins
Keyword(s):  
Endoplasmic Reticulum ◽  
Uniform Distribution ◽  
Specific Activity ◽  
Intact Cell ◽  
Smooth Endoplasmic Reticulum ◽  
Membrane Phospholipid ◽  
Phospholipid Synthesis ◽  
Protein Ratio ◽  
Cytochemical Localization ◽  
Heterogeneous Distribution

During proliferation of smooth endoplasmic reticulum (SER) induced by phenobarbital the specific activity of acyltransferases of the smooth microsomes increases, there is a transient rise in the phospholipid/protein ratio of these membranes, and an increased incorporation of [14C]glycerol into smooth-membrane phospholipid. Microsomes separated into subfractions on 2 gradients exhibited a heterogeneous distribution of these characteristics, indicating a non-uniform distribution of the site of phospholipid synthesis in the ER under these conditions. Cytochemical localization of acyltransferases on whole liver and smooth and rough microsomes confirmed this heterogeneity, and indicated that the distribution of this activity was not restricted to any morphologically distinct site in the ER of the intact cell. After 4 days of phenobarbital treatment the increased membrane is restricted to lighter subfractions and is similar in distribution to that of increased acyltransferase activity. These results indicate that the synthesis of membrane phospholipid and the growth of the SER in response to phenobarbital is not uniform but occurs at randomly dispersed sites in the SER while proteins may be added preferentially at these sites resulting in a final uniform distribution.

scholarly journals The disulphide-bonded nature of procollagen and the role of the extension peptides in the assembly of the molecule

1977 ◽  
Vol 161 (2) ◽  
pp. 405-418 ◽  
Author(s):  
R Harwood ◽  
A H Merry ◽  
D E Woolley ◽  
M E Grant ◽  
D S Jackson
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Gel Filtration ◽  
Close Correlation ◽  
Helical Conformation ◽  
Composite Gels ◽  
Tendon Cells ◽  
Cartilage Cells ◽  
And Cartilage

1. The molecular weights of chick tendon and cartilage procollagens, and their constituent polypeptides, were determined by gel filtration and gel electrophoresis. The values obtained are in good agreement and indicate that the mol.wts. of the secreted procollagens (types I and II) and their individual pro-alpha-chains are of the order of 405 000-445 000 and 137 000-145 000 respectively.2. Digestion of tendon procollagen with human rheumatoid synovial collagenase gave products consistent with the presence of large non-helical peptide extensions at both N-and C-termini. Electrophoretic analysis gave apparent mol.wts. of 17 500 and 36 000 for the respective N- and C-terminal extensions of pro-alpha1(I)-and pro-alpha2-chains, and inter-chain disulphide bonds were restricted to the C-terminal location. 3. During the biosynthesis of procollagen by tendon and cartilage cells a close correlation was observed between the extent of inter-chain disulphide bonding and the proportion of procollagen polypeptides having a triple-helical conformation. These processes appeared to commence in the rough endoplasmic reticulum and be completed in the smooth endoplasmic reticulum, but the rate at which they occur in cartilage cells is markedly slower than that found in tendon cells. 4. When the intracellular [14C]procollagen polypeptides present in the rough-endoplasmic-reticulum fractions of tendon and cartilage cells were analysed under non-reducing conditions on agarose/polyacrylamide composite gels, no significant pools of dimeric intermediates were detected. 5. In both cell types, inter-chain disulphide-bond formation occurred even when hydroxylation, and hence triple-helix formation, was inhibited. The presence of pro-alpha1- and pro-alpha2-components in a ratio of 2:1 in the disulphide-linked unhydroxylated procollagen isolated from tendon cells demonstrated that correct chain association occurs in the absence of hydroxylation. This observation is consistent with a model for the assembly of pro-gamma112-chains in which the recognition and selection of pro-alpha1-and pro-alpha2-chains in a 2:1 ratio are directed by the non-helical C-terminal extension peptides of tendon procollagen.

Induction of cytochrome P-450 in a selective subpopulation of hepatocytes

1978 ◽  
Vol 234 (3) ◽  
pp. C102-C109 ◽  
Author(s):  
J. J. Gumucio ◽  
L. J. DeMason ◽  
D. L. Miller ◽  
S. O. Krezoski ◽  
M. Keener
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Inductive Effect ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Cell Subpopulation ◽  
Continuous Density ◽  
Liver Cytochrome ◽  
Cytochrome P 450 ◽  
In Cells

The objective of this study was to determine whether the inductive effect of phenobarbital (PB) on liver cytochrome P-450 was the result of the action of this drug on all or some hepatocytes. For this purpose, a light (cell band I) and a heavy (cell band II) subpopulation of hepatocytes were separated from rat liver in a continuous density gradient. To determine the location of these hepatocytes in tissue, [14C]bromobenzene, which binds covalently to centrilobular hepatocytes, was administered. The specific activity (14C dpm/mg protein) was greater in cells of band I than in cells of band II, suggesting a predominant contribution of centrilobular hepatocytes to the lighter cell band. Microsomes were separated from each cell subpopulation after 3 days of PB administration and cytochrome P-450 was measured. Although a fivefold increment in cytochrome P-450 content of light hepatocytes was noted, the content of heavy hepatocytes was similar to that of the respective subpopulation in controls. Concomitantly, PB administered for 3 days induced the smooth endoplasmic reticulum of centrilobular hepatocytes only, as revealed by electron microscopy of whole tissue. These results indicated that PB induces cytochrome P-450 in a selective subpopulation of hepatocytes, most likely located near the terminal hepatic venule.

scholarly journals Polyribosomal attachment to rat liver and hepatoma endoplasmic reticulum in vitro. A method for its study

1971 ◽  
Vol 121 (2) ◽  
pp. 271-278 ◽  
Author(s):  
W. L. Ragland ◽  
T. K. Shires ◽  
H. C. Pitot
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Citric Acid ◽  
Low Temperature ◽  
Rough Endoplasmic Reticulum ◽  
Half Life ◽  
Binding Capacity ◽  
Smooth Endoplasmic Reticulum ◽  
Quantitative Separation

A system for study and measurement of the attachment in vitro of exogenous polyribosomes to membranes has been presented. Its main features are use of low temperature, post-microsomal supernatant, pyrophosphate and citric acid to remove ribosomes from the surface of rough endoplasmic reticulum, and a method for quantitative separation of unattached from membrane-associated polyribosomes. The following were found. (1) Rough endoplasmic reticulum, from which ribosomes had been removed by treatment with pyrophosphate and citrate, bound over 50% of added polyribosomes, whereas the untreated (or control) rough and smooth endoplasmic reticulum and the smooth endoplasmic reticulum treated with pyrophosphate–citrate did not bind polyribosomes. (2) The polyribosome-binding capacity of rough endoplasmic reticulum stripped of its ribosomes decayed upon storage of the membranes at 0–4°C. The half-life of this decay was about 6 days whereas that of the polyribosome-binding capacity of hepatoma stripped rough endoplasmic reticulum was about 1.5 days. (3) Preparations of stripped rough endoplasmic reticulum after reassociation with polyribosomes in vitro were quite similar to preparations of native rough endoplasmic reticulum as viewed with the electron microscope. Evidence is presented to support the contention that association of polyribosomes with membranes was the result of polyribosomal reattachment to the membranes rather than trapping of the polyribosomes between vesicles of the membranes.

scholarly journals Studies on the glycosylation of hydroxylysine residues during collagen biosynthesis and the subcellular localization of collagen galactosyltransferase and collagen glucosyltransferase in tendon and cartilage cells

1975 ◽  
Vol 152 (2) ◽  
pp. 291-302 ◽  
Author(s):  
Richard Harwood ◽  
Michael E. Grant ◽  
David S. Jackson
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Specific Activity ◽  
Smooth Endoplasmic Reticulum ◽  
Gradient Centrifugation ◽  
Subcellular Fractions ◽  
Anterior Lens Capsule ◽  
Cartilage Cells ◽  
Membrane Bound ◽  
And Cartilage

1. The glycosylation of hydroxylysine during the biosynthesis of procollagen by embryonic chick tendon and cartilage cells was examined. When free and membrane-bound ribosomes isolated from cells labelled for 4min with [14C]lysine were assayed for hydroxy[14C]lysine and hydroxy[14C]lysine glycosides, it was found that hydroxylation took place only on membrane-bound ribosomes and that some synthesis of galactosylhydroxy[14C]lysine and glucosylgalactosylhydroxy[14C]lysine had occurred on the nascent peptides. 2. Assays of subcellular fractions isolated from tendon and cartilage cells labelled for 2h with [14C]lysine demonstrated that the glycosylation of procollagen polypeptides began in the rough endoplasmic reticulum. 14C-labelled polypeptides present in the smooth endoplasmic reticulum and Golgi fractions were glycosylated to extents almost identical with the respective secreted procollagens. 3. Assays specific for collagen galactosyltransferase and collagen glucosyltransferase are described, using as substrate chemically treated bovine anterior-lens-capsule collagen. 4. When homogenates were assayed for the collagen glycosyltransferase activities, addition of Triton X-100 (0.01%, w/v) was found to stimulate enzyme activities by up to 45%, suggesting that the enzymes were probably membrane-bound. 5. Assays of subcellular fractions obtained by differential centrifugation for collagen galactosyltransferase activity indicated the specific activity to be highest in the microsomal fractions. Similar results were obtained for collagen glucosyltransferase activity. 6. When submicrosomal fractions obtained by discontinuous-sucrose-density-gradient-centrifugation procedures were assayed for these enzymic activities, the collagen galactosyltransferase was found to be distributed in the approximate ratio 7:3 between rough and smooth endoplasmic reticulum of both cell types. Similar determinations of collagen glucosyltransferase indicated a distribution in the approximate ratio 3:2 between rough and smooth microsomal fractions. 7. Assays of subcellular fractions for the plasma-membrane marker 5′-nucleotidase revealed a distribution markedly different from the distributions obtained for the collagen glycosyltransferase. 8. The studies described here demonstrate that glycosylation occurs early in the intracellular processing of procollagen polypeptides rather than at the plasma membrane, as was previously suggested.

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