Effect of Adrenalectomy and of Adrenocortical Hormones on RNA Turnover in a Variety of Subcellular Fractions of Rat Liver

1973 ◽  
Vol 51 (6) ◽  
pp. 920-930 ◽  
Author(s):  
R. K. Mishra ◽  
L. A. W. Feltham
Keyword(s):  
Endoplasmic Reticulum ◽  
Steady State ◽  
Rat Liver ◽  
Orotic Acid ◽  
Turnover Rate ◽  
Single Injection ◽  
Smooth Endoplasmic Reticulum ◽  
Rna Turnover ◽  
Liver Nuclei ◽  
Adrenalectomized Rats

(1) The turnover of RNA was examined by following the loss of radioactivity after a single injection of 14C-orotic acid in nuclei, mitochondria, smooth endoplasmic reticulum, rough endoplasmic reticulum, free polysomes, total ribosomes, and sRNA from rat liver. The half-lives of the RNA of various rat liver fractions were found to be 8.7, 6.5, 6.4, 5.4, 4.4, 4.9, and 4.8 days, respectively.(2) In adrenalectomized rats there was a significant decrease in turnover rate. This suggests a slower synthesis of RNA under steady-state conditions. The corresponding values were 12.0, 8.5, 6.5, 6.9, 5.8, 6.1, and 5.9 days.(3) Daily administration of corticosterone or hydrocortisone to adrenalectomized rats restored the turnover rate to normal. Aldosterone was without effect.(4) Aggregate RNA polymerase of rat liver nuclei was decreased by adrenalectomy and restored by corticosterone or hydrocortisone. Aldosterone was without effect.

scholarly journals Subpopulations of proteasomes in rat liver nuclei, microsomes and cytosol

1996 ◽  
Vol 316 (2) ◽  
pp. 401-407 ◽  
Author(s):  
Amparo PALMER ◽  
A. Jennifer RIVETT ◽  
Stuart THOMSON ◽  
Klavs B. HENDIL ◽  
Geoffrey W. BUTCHER ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Immunoblot Analysis ◽  
Cell Compartments ◽  
Histocompatibility Complex ◽  
Distinct Cell ◽  
Liver Nuclei ◽  
High Concentrations ◽  
Α Subunits

Mammalian proteasomes are composed of 14–17 different types of subunits, some of which, including major-histocompatibility-complex-encoded subunits LMP2 and LMP7, are non-essential and present in variable amounts. We have investigated the distribution of total proteasomes and some individual subunits in rat liver by quantitative immunoblot analysis of purified subcellular fractions (nuclei, mitochondria, microsomes and cytosol). Proteasomes were mainly found in the cytosol but were also present in the purified nuclear and microsomal fractions. In the nuclei, proteasomes were soluble or loosely attached to the chromatin, since they could be easily extracted by treatment with nucleases or high concentrations of salt. In the microsomes, proteasomes were on the outside of the membranes. Further subfractionation of the microsomes showed that the proteasomes in this fraction were associated with the smooth endoplasmic reticulum and with the cis-Golgi but were practically absent from the rough endoplasmic reticulum. Using monospecific antibodies for some proteasomal subunits (C8, C9, LMP2 and Z), the composition of proteasomes in nuclei, microsomes and cytosol was investigated. Although there appear not to be differences in proteasome composition in the α subunits (C8 and C9) in the different locations, the relative amounts of some β subunits varied. Subunit Z was enriched in nuclear proteasomes but low in microsome-asssociated proteasomes, whereas LMP2, which was relatively low in nuclei, showed a small enrichment in the microsomes. These differences in subunit composition of proteasomes probably reflect differences in the function of proteasomes in distinct cell compartments.

Studies on the site of addition of sialic acid and glucosamine to rat α1-acid glycoprotein

1977 ◽  
Vol 55 (4) ◽  
pp. 408-414 ◽  
Author(s):  
J. C. Jamieson
Keyword(s):  
Endoplasmic Reticulum ◽  
Sialic Acid ◽  
Rat Liver ◽  
Golgi Complex ◽  
Smooth Endoplasmic Reticulum ◽  
Main Site ◽  
Acid Glycoprotein ◽  
Membrane Bound ◽  
Polypeptide Chains

Ultrasonic extracts of rough and smooth endoplasmic reticulum fractions and Golgi fractions from rat liver were examined by immunoelectrophoresis using antiserum to α1-acid glycoprotein. Rough endoplasmic reticulum fractions contained only sialic acid free α1-acid glycoprotein, whereas smooth endoplasmic reticulum and Golgi fractions also contained sialic acid containing α1-acid glycoprotein. Determination of the sialic acid contents of immune precipitates isolated from the extracts suggested that the Golgi complex was the main site of addition of sialic acid to α1-acid glycoprotein. Immunological studies on puromycin extracts of polyribosomes showed that polypeptide chains of α1-acid glycoprotein and albumin were assembled mainly on membrane-bound polyribosomes. Evidence is presented from incorporation studies with labelled leucine and glucosamine that initial glycosylation of α1-acid glycoprotein occurs mainly or entirely after release of nascent polypeptide from the ribosomal site.

scholarly journals Immunocytochemical localization of lysosomal beta-galactosidase in rat liver.

1983 ◽  
Vol 97 (5) ◽  
pp. 1559-1565 ◽  
Author(s):  
P M Novikoff ◽  
N F La Russo ◽  
A B Novikoff ◽  
R J Stockert ◽  
A Yam ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Protein A ◽  
Intracellular Sorting ◽  
Specialized Region ◽  
Beta Galactosidase ◽  
Specific Polyclonal Antibody ◽  
Galactosyl Residues

beta-galactosidase is a ubiquitous lysosomal hydrolase that specifically cleaves terminal beta-galactosyl residues from glycoproteins, glycosaminoglycans, oligosaccharides, and glycolipids. To study the intracellular distribution of this enzyme, we prepared a specific polyclonal antibody to lysosomal beta-galactosidase by immunizing rabbits with a highly purified preparation of beta-galactosidase from rat liver. Using this antibody we employed an immunocytochemical technique (protein A coupled to horseradish peroxidase and diaminobenzidine cytochemistry) and showed that beta-galactosidase is present in all hepatocytes of the rat liver. All types of lysosomes, the rough endoplasmic reticulum, and the specialized region of smooth endoplasmic reticulum known as GERL showed immunoreactivity. This in situ distribution suggests that these organelles are involved in the biosynthesis and intracellular sorting of this lysosomal enzyme.

scholarly journals Properties of membrane-bound bilirubin UDP-glucuronyltransferase in rough and smooth endoplasmic reticulum and in the nuclear envelope from rat liver

1989 ◽  
Vol 259 (3) ◽  
pp. 659-663 ◽  
Author(s):  
F Vanstapel ◽  
L Hammaker ◽  
K Pua ◽  
N Blanckaert
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Membrane System ◽  
Permeability Barrier ◽  
Membrane Bound ◽  
Marker Studies ◽  
High Degree ◽  
Regulatory Properties

We examined regulatory properties of bilirubin UDP-glucuronyltransferase in sealed RER (rough endoplasmic reticulum)- and SER (smooth endoplasmic reticulum)-enriched microsomes (microsomal fractions), as well as in nuclear envelope from rat liver. Purity of membrane fractions was verified by electron microscopy and marker studies. Intactness of RER and SER vesicles was ascertained by a high degree of latency of the lumenal marker mannose-6-phosphatase. No major differences in the stimulation of UDP-glucuronyltransferase by detergent or by the presumed physiological activator, UDPGlcNAc, were observed between total microsomes and RER- or SER-enriched microsomes. Isolated nuclear envelopes were present as a partially disrupted membrane system, with approx. 50% loss of mannose-6-phosphatase latency. The nuclear transferase had lost its latency to a similar extent, and the enzyme failed to respond to UDPGlcNAc. Our results underscore the necessity to include data on the integrity of the membrane permeability barrier when reporting regulatory properties of UDP-glucuronyltransferase in different membrane preparations.

scholarly journals Phospholipid synthesis in rat liver endoplasmic reticulum after the administration of phenobarbitone and 20-methylcholanthrene

1974 ◽  
Vol 142 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Susan C. Davison ◽  
Eric D. Wills
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Turnover Rate ◽  
Total Phospholipid ◽  
Transient Increase ◽  
Phospholipid Synthesis ◽  
Phosphatidylethanolamine Methyltransferase ◽  
Phosphatidylcholine Synthesis

1. Phenobarbitone injection did not affect the concentration of phospholipids in the liver endoplasmic reticulum, but it increased the rate of incorporation of [32P]orthophosphate into the phospholipids. 20-Methylcholanthrene caused a transient increase in total phospholipid but a decrease in the turnover rate of the phospholipids. 2. Incorporation of [32P]orthophosphate into phosphatidylcholine, compared with that into phosphatidylethanolamine, was increased by phenobarbitone injection but decreased by 20-methylcholanthrene injection. 3. The activity of S-adenosylmethionine–phosphatidylethanolamine methyltransferase increased 12h after phenobarbitone injection, when incorporation of [32P]orthophosphate into phosphatidylcholine was a maximum, but at other times, and after 20-methylcholanthrene injection, the activity of the enzyme did not correlate with the rate of phosphatidylcholine synthesis. 4. [14C]Glycerol was incorporated more rapidly into phosphatidylcholine than into phosphatidylethanolamine, whereas [32P]orthophosphate and [14C]ethanolamine were incorporated more rapidly into phosphatidylethanolamine than into phosphatidylcholine. 5. Incorporation of [32P]orthophosphate into phosphatidylethanolamine of liver slices incubated in vitro was much more rapid than into phosphatidylcholine, and incorporation into phosphatidylcholine was markedly stimulated by addition of methionine to the medium. Changes in the incorporation of [32P]orthophosphate into phospholipids observed in vivo after injection of phenobarbitone or methylcholanthrene could not be reproduced in slices incubated in vitro. 6. It is concluded that phenobarbitone injection causes an increased rate of turnover of total phospholipids in the endoplasmic reticulum and an increased conversion of phosphatidylethanolamine into phosphatidylcholine, whereas 20-methylcholanthrene injection depresses both the turnover rate of total phospholipids and the formation of phosphatidylcholine.

scholarly journals ISOLATION OF TWO DISTINCT CLASSES OF POLYSOMES FROM A NUCLEAR FRACTION OF RAT LIVER

1968 ◽  
Vol 37 (1) ◽  
pp. 163-181 ◽  
Author(s):  
Paul D. Sadowski ◽  
Janet Alcock Howden
Keyword(s):  
Outer Membrane ◽  
Rat Liver ◽  
Orotic Acid ◽  
Specific Activity ◽  
Nuclear Fraction ◽  
Differential Centrifugation ◽  
Rat Liver Nuclei ◽  
Liver Nuclei ◽  
Triton X

Isolated rat liver nuclei were washed with Triton-X-100 in the presence of liver cell sap. This treatment liberated a fraction of polysomes which were isolated by differential centrifugation and were designated "outer membrane polysomes." The outer membrane polysomes synthesized protein in vivo. Shortly after injection of orotic acid-14C, the RNA of outer membrane polysomes had a higher specific activity than that of cytoplasmic polysomes. It was postulated that outer membrane polysomes may be an intermediate in the transfer of newly synthesized RNA from the nucleus to the cytoplasm. In other experiments, Triton-washed rat liver nuclei were lysed in the presence of deoxycholate and deoxyribonuclease. A ribonucleoprotein fraction was isolated from the lysate by differential centrifugation. This fraction contained "intranuclear ribosomes," which sedimented like partially degraded polysomes in sucrose gradients. This degradation could be partially prevented if intranuclear ribosomes were purified by sedimentation through heavy sucrose. The resulting pellets were termed "intranuclear polysomes" because they contained some undergraded polysomes. Intranuclear polysomes were highly radioactive after a brief pulse with orotic acid-14C, but did not appear to synthesize protein rapidly in vivo. Intranuclear polysomes may represent the initial stage of assembly of polyribosomes in the nucleus.

Sign in / Sign up

Export Citation Format

Share Document