scholarly journals Phenylhydrazine-mediated induction of haem oxygenase activity in rat liver and kidney and development of hyperbilirubinaemia. Inhibition by zinc-protoporphyrin

1984 ◽  
Vol 217 (2) ◽  
pp. 409-417 ◽  
Author(s):  
M D Maines ◽  
J C Veltman
Keyword(s):  
Rat Liver ◽  
Zinc Protoporphyrin ◽  
Serum Total Bilirubin ◽  
Potent Inducer ◽  
Oxygenase Activity ◽  
Liver And Kidney ◽  
Haem Oxygenase ◽  
Cytochrome P 450

Phenylhydrazine was found to be a potent inducer of microsomal haem oxygenase activity in rat liver and kidney, but not in spleen. The phenylhydrazine-mediated increase in haem oxygenase activity was time-dependent. Maximum activity was attained 12h after treatment in the liver, and 24h after treatment in the kidney. The increases in the activity of haem oxygenase in the liver and the kidney could be inhibited by cycloheximide. Furthermore, the increases could not be elicited by the treatment of microsomal preparations in vitro with phenylhydrazine. In consonance with the increased haem oxygenase activity, a marked increase (16-fold) was observed in the serum total bilirubin concentration in phenylhydrazine-treated rats. The mechanism of haem degradation promoted by phenylhydrazine in vivo appears to differ from that in vitro; only in the former case is bilirubin formed as the end-product of haem degradation. When rats were given zinc-protoporphyrin (40 mumol/kg) 12h before and after phenylhydrazine treatment, the phenylhydrazine-mediated increases in haem oxygenase activity in the liver and the kidney were effectively blocked. Treatment of rats in vivo with the metalloporphyrin also inhibited the activity of splenic haem oxygenase, and promoted a major decrease in the serum bilirubin levels. In phenylhydrazine-treated animals, the microsomal content of cytochrome P-450 was significantly decreased in the absence of a decrease in the microsomal haem concentration. The decrease in cytochrome P-450 content was accompanied by an increased absorption in the 420nm region of the reduced CO-difference spectrum, suggesting the conversion of the cytochrome to an inactive form. The marked depletion of cellular glutathione levels suggests that this conversion may be related to the action of active intermediates and free radicals formed in the course of the interaction of phenylhydrazine with the haem moiety of cytochrome P-450.

scholarly journals Degradation of cytochrome P-450 haem by carbon tetrachloride and 2-allyl-2-isopropylacetamide in rat liver in vivo and in vitro. Involvement of non-carbon monoxide-forming mechanisms

1979 ◽  
Vol 184 (3) ◽  
pp. 481-489 ◽  
Author(s):  
Philip S. Guzelian ◽  
Robert W. Swisher
Keyword(s):  
Lipid Peroxidation ◽  
Free Radicals ◽  
Carbon Tetrachloride ◽  
Pulse Labelling ◽  
Forming Mechanism ◽  
Oxygenase Activity ◽  
Haem Oxygenase ◽  
Cytochrome P 450

Degradation of intrinsic hepatic [14C]haem was analysed as 14CO formation in living rats and in hepatic microsomal fractions prepared from these animals 16h after pulse-labelling with 5-amino[5-14C]laevulinic acid, a precursor that labels bridge carbons of haem in non-erythroid tissues. NADPH-catalysed peroxidation of microsomal lipids in vitro (measured as malondialdehyde) was accompanied by loss of cytochrome P-450 and microsome-associated [14C]haem (largely cytochrome P-450 haem), but little 14CO formation. No additional 14CO was formed when carbon tetrachloride and 2-allyl-2-isopropylacetamide were added to stimulate lipid peroxidation and increase loss of cytochrome P-450 [14C]haem. Because the latter effect persisted despite inhibition of lipid peroxidation with MnCl2 or phenyl-t-butylnitrone(a spin-trapping agent for free radicals), it was concluded that carbon tetrachloride, as reported for 2-allyl-2-isopropylacetamide, may promote loss of cytochrome P-450 haem through a non-CO-forming mechanism independent of lipid peroxidation. By comparison with breakdown of intrinsic haem, catabolism of [14C]methaemalbumin by microsomal haem oxygenase in vitro produced equimolar quantities of 14CO and bilirubin, although these catabolites reflected only 18% of the degraded [14C]haem. This value was increased to 100% by addition of MnCl2, which suggests that lipid peroxidation may be involved in degradation of exogenous haem to products other than CO. Phenyl-t-butylnitrone completely blocked haem oxygenase activity, which suggests that hydroxy free radicals may represent a species of active oxygen used by this enzyme system. After administration of carbon tetrachloride or 2-allyl-2-isopropylacetamide to labelled rats, hepatic [14C]haem was decreased and haem oxygenase activity was unchanged; however, 14CO excretion was either unchanged (carbon tetrachloride) or decreased (2-allyl-2-isopropylacetamide). These changes were unaffected by cycloheximide pretreatment. From the lack of parallel losses of cytochrome P-450 [14C]haem and 14CO excretion, one may infer that an important fraction of hepatic [14C]haem in normal rats is degraded by endogenous pathways not involving CO. We conclude that carbon tetrachloride and 2-allyl-2-isopropylacetamide accelerate catabolism of cytochrome P-450 haem through mechanisms that do not yield CO as an end product, and that are insensitive to cycloheximide and independent of haem oxygenase activity.

The protective properties of synthetic porphyrin tin complexes in toxic hyperbilirubinemia

2000 ◽  
Vol 04 (03) ◽  
pp. 243-247 ◽  
Author(s):  
T. O. PHILIPPOVA ◽  
B. N. GALKIN ◽  
N. YA. GOLOVENKO ◽  
Z. I. ZHILINA ◽  
S. V. VODZINSKII
Keyword(s):  
Heme Oxygenase ◽  
Serum Bilirubin ◽  
Protoporphyrin Ix ◽  
Serum Bilirubin Level ◽  
Oxygenase Activity ◽  
Tetraphenyl Porphyrin ◽  
Tin Complexes ◽  
Cytochrome P 450

Tin complexes of meso-substituted synthetic porphyrins, namely Sn 4+-meso-tetraphenyl- porphyrin ( Sn - TPP ) and Sn 4+-meso-tetrakis(N-methyl-3-pyridyl)porphyrin tetratosylate ( Sn - TMe -3- PyP ), efficiently decrease the serum bilirubin level when injected subcutaneously at a dose of 100 μM kg−1 body weight into mice. These compounds are active during hyperbilirubinemia, induced by phenylhydrazine, hemin and tetrachloromethane, and also during autoimmune hemolytic anemia. In the latter case a decrease in serum bilirubin content was observed, as well as a decrease in the amount of blood reticulocytes which reflects a milder course of the disease. The Sn complexes under study induce, in vivo, cytochrome P-450, inhibit microsomal heme oxygenase and decrease the intensity of lipid peroxidation. At the same time, in vitro the hepatic and splenic heme oxygenase activity is blocked only when a 0.1 μM concentration of Sn - TMe -3- PyP or Sn -protoporphyrin IX is added to the incubation mixture. Sn - TPP does not affect the activity of this enzyme in vitro.

Studies on the Biosynthesis of Flavin Nucleotides from 2-14C-Riboflavin by Rat Liver and Kidney

1973 ◽  
Vol 51 (6) ◽  
pp. 772-782 ◽  
Author(s):  
A. G. Fazekas ◽  
T. Sandor
Keyword(s):  
Rat Liver ◽  
Flavin Adenine Dinucleotide ◽  
Total Radioactivity ◽  
Flavin Mononucleotide ◽  
Time Intervals ◽  
Adult Rats ◽  
Liver And Kidney ◽  
Rat Liver Cytosol

2-14C-Riboflavin was injected subcutaneously into young adult rats to study the biosynthesis of flavin mononucleotide (FMN) and flavin–adenine dinucleotide (FAD) in the liver and kidneys. Animals were sacrificed at different time intervals following the administration of labelled riboflavin (RF), and radioactive flavins were determined in their tissues by a newly devised method. Both tissues accumulated radioactive riboflavin rapidly and peak levels were obtained at 90 min after the injection, when over 80% of the total radioactivity of the liver was present in FAD. At this time the liver contained 17% of the injected dose of 2-14C-RF. The kidneys contained relatively high quantities of free RF due to the concentration and urinary excretion of the vitamin.Analysis of subcellular fractions of the liver of animals injected with 2-14C-RF revealed that most of the radioactivity was present in mitochondria and nuclei. The flavin nucleotides of rat liver cytosol became progressively associated with macromolecules in vivo. However, there was no significant binding of free RF by macromolecules in blood plasma or liver cytosol.Kinetic studies and incubations with liver slices indicated that RF freely diffuses into the liver cells, is rapidly converted into FAD, and becomes attached to apoenzymes. The tissue uptake of RF and FMN formation is considerably influenced by the concentration of RF present in the system, both in vivo and in vitro.

scholarly journals Effect of endotoxin on tryptophan pyrrolase and delta-aminolaevulinate synthase: evidence for an endogenous regulatory haem fraction in rat liver

1977 ◽  
Vol 166 (2) ◽  
pp. 301-304 ◽  
Author(s):  
D M Bissell ◽  
L E Hammaker
Keyword(s):  
Rat Liver ◽  
Peak Activity ◽  
Endotoxin Administration ◽  
Oxygenase Activity ◽  
Tryptophan Pyrrolase ◽  
Haem Oxygenase ◽  
Enzyme Functions ◽  
New Evidence ◽  
Cytochrome P 450

Endotoxin was administered to rats at a dose shown previously to stimulate hepatic haem oxygenase activity and to block induction of delta-aminolaevulinate synthase, apparently by causing redistribution of haem from cytochrome P-450 to a regulatory haem pool in the liver. Within 5h of the administration of endotoxin (at a time when the effect of the compound on cytochrome P-450 is maximal) the relative saturation of tryptophan pyrrolase with intrinsic haem rose, from a basal value of 50% to 90%, indicating that ‘free’ haem had become available. Concurrently, the activity of delta-aminolaevulinate synthase was decreased to 25% of its basal value. Haem oxygenase reached peak activity 13h after endotoxin administration. These findings provide new evidence for the existence of an ‘unassigned’ hepatic haem fraction, which exchanges with cytochrome P-450 haem and regulates these three enzyme functions.

scholarly journals Effect of a single dose of dimethylnitrosamine on biosynthesis of nucleic acid and protein in rat liver and kidney

1971 ◽  
Vol 125 (4) ◽  
pp. 943-952 ◽  
Author(s):  
B. W. Stewart ◽  
P. N. Magee
Keyword(s):  
Single Dose ◽  
Rat Liver ◽  
Sucrose Density Gradient ◽  
Polymerase Activity ◽  
Hepatic Necrosis ◽  
Deficient Diet ◽  
Morphological Studies ◽  
Liver And Kidney

1. Administration of a single dose of dimethylnitrosamine to rats temporarily fed on a protein-deficient diet causes a high incidence of kidney tumours. The effect of such a dose of dimethylnitrosamine (40mg/kg body wt.) on metabolism of nucleic acids and protein in rat liver and kidneys was examined during the week immediately after administration. 2. Incorporation of [14C]leucine and [14C]orotate into hepatic macromolecules was inhibited within 5h of injection of dimethylnitrosamine, and did not recover for at least 5 days. Interpretation of these results is complicated by the concomitant extensive hepatic necrosis. 3. Renal RNA synthesis was assayed by incorporation of [14C]orotate in vivo and measurement of DNA-dependent RNA polymerase activity in vitro. Both systems indicate biphasic inhibition; minimal activity was recorded 9h and 3 days after treatment. Changes in incorporation of [14C]leucine into renal protein were similar but less marked. 4. Sucrose-density-gradient analysis of renal cytoplasmic RNA indicated increased synthesis of rRNA 24h after injection of the nitrosamine. The rate of loss of radioactivity from kidney ribosomes pre-labelled with [14C]orotate was not modified by dimethylnitrosamine. 5. Dimethylnitrosamine increased incorporation of [3H]-thymidine into renal DNA. The three distinct periods of stimulated synthesis observed are discussed, with particular reference to recently published morphological studies of the sequential development of kidney tumours induced by dimethylnitrosamine in protein-depleted rats.

scholarly journals Metabolism of a glutathione conjugate of 2-hydroxyoestradiol by rat liver and kidney preparations in vitro

1970 ◽  
Vol 116 (5) ◽  
pp. 913-917 ◽  
Author(s):  
John S. Elce
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Male Rat ◽  
Amino Group ◽  
Glutathione Conjugate ◽  
Acetyl Coenzyme A ◽  
Adult Male Rat ◽  
Liver And Kidney

Adult male rat liver and kidney preparations were incubated with (2-hydroxyoestradiol-1-yl)[35S]glutathione. The glutamic acid and glycine residues were removed by enzymes present in the kidney microsomal fraction; the liver preparations had no effect. The resulting 2-hydroxyoestradiol–cysteine conjugate was acetylated at the α-amino group by both liver and kidney homogenates fortified with acetyl-coenzyme A, but not significantly in the absence of this coenzyme, or by liver or kidney slices. These results suggest that an oestrogen–glutathione conjugate, if formed in vivo, would be converted into the corresponding mercapturic acid before excretion.

scholarly journals The cytochromes in microsomal fractions of germinating mung beans

1981 ◽  
Vol 194 (3) ◽  
pp. 743-751 ◽  
Author(s):  
G A F Hendry ◽  
J D Houghton ◽  
O T G Jones
Keyword(s):  
Cytochrome B ◽  
Mung Bean ◽  
Microsomal Fraction ◽  
Degradation Mechanism ◽  
Cytochrome B5 ◽  
Rapid Degradation ◽  
Haem Oxygenase ◽  
Cytochrome P 450

Detailed studies of microsomal cytochromes from mung-bean radicles showed the presence of cytochrome P-420, particularly in dark-grown seedlings, accompanied by smaller quantities of cytochrome P-450. Similar proportions of cytochrome P-420 to cytochrome P-450 were found spectrophotometrically in vivo with whole radicles and hypocotyls. Assayed in vitro, maximum concentrations of both cytochromes were attained after 4 days of growth, before undergoing rapid degradation. Illumination of seedlings stabilized cytochrome P-450 and decreased the amount of cytochrome P-420. Three b cytochromes were present in the microsomal fraction, namely cytochromes b-562.5 (Em + 105 +/- 23 mV), b-560.5 (Em + 49 +/- 13 mV) and b5 (Em - 45 +/- 14 mV), all at pH 7.0. Of the b cytochromes, cytochrome b5 alone undergoes a rapid degradation after day 4, Changes in cytochrome b concentrations were confined to the microsomal fraction: mitochondrial b cytochrome concentrations were unaltered with age. Protohaem degradation (of exogenous methaemalbumin) was detected in microsomal fractions of mung beans. The rates of degradation were highest in extracts of young tissue and declined after day 4. The degradation mechanism and products did not resemble those of mammalian haem oxygenase.

Characterization of a novel non-peptide vasopressin V1 receptor antagonist (OPC-21268) in the rat

1993 ◽  
Vol 138 (2) ◽  
pp. 259-266 ◽  
Author(s):  
L. M. Burrell ◽  
P. A. Phillips ◽  
J. Stephenson ◽  
J. Risvanis ◽  
A.-M. Hutchins ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Rat Liver ◽  
Renal Medulla ◽  
Kinetic Studies ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Liver And Kidney

ABSTRACT A non-peptide, orally effective, vasopressin (AVP) V1 receptor antagonist 1-{1-[4-(3-acetylaminopropoxy) benzoyl]-4-piperidyl}-3,4-dihydro-2(1H)-quinolinone (OPC-21268) has recently been described. This paper reports the in-vitro and in-vivo characterization of OPC-21268 binding to vasopressin receptors in rat liver and kidney. OPC-21268 caused a concentration-dependent displacement of the selective V1 receptor antagonist radioligand, 125I-labelled [d(CH2)5,sarcosine7]AVP to V1 receptors in both rat liver and kidney medulla membranes. The concentration of OPC-21268 that displaced 50% of specific AVP binding (IC50) was 40±3 nmol/l for liver V1 and 15±2 nmol/l for kidney V1 receptors (mean ± s.e.m.; n = 3). OPC-21268 had little effect on the selective V2 antagonist radioligand [3H]desGly-NH29[d(CH2)5,d-Ile2,Ile4] AVP binding to V2 receptors in renal medulla membranes (IC50 >0·1 mmol/l). After oral administration to rats, OPC-21268 was an effective V1 antagonist in a time- and dose-dependent manner. Binding kinetic studies showed that OPC-21268 acted as a competitive antagonist at the liver V1 receptor in vitro and in vivo, in addition to its in-vitro competitive effects at the renal V1 receptor. OPC-21268 shows promise as an orally active V1 antagonist. Journal of Endocrinology (1993) 138, 259–266

Sign in / Sign up

Export Citation Format

Share Document