scholarly journals BENZPYRENE HYDROXYLASE ACTIVITY IN ISOLATED PARENCHYMAL AND NONPARENCHYMAL CELLS OF RAT LIVER

1972 ◽  
Vol 52 (2) ◽  
pp. 316-321 ◽  
Author(s):  
Elroy Cantrell ◽  
Edward Bresnick
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Steroid Metabolism ◽  
Hydroxylase Activity ◽  
Adult Rats ◽  
Polycyclic Hydrocarbons ◽  
Nonparenchymal Cells ◽  
Parenchymal Cells ◽  
Benzpyrene Hydroxylase

Previous studies have implicated the reticuloendothelial cells of the liver in certain aspects of steroid metabolism. The similarity in the metabolism of steroids and polycyclic hydrocarbons suggested that the nonparenchymal cells possibly play a role in these areas. The present study presents evidence that at least one of the microsomal NADPH-requirig enzymes, benzpyrene hydroxylase, is present in nonparenchymal cells and, furthermore, is "inducible." In adult rats treated with 3-methylcholanthrene or ß-naphthoflavone, the nonparenchymal cells exhibited increases in benzpyrene hydroxylase activity of 17-fold and five-fold, respectively. Treatment with phenobarbital resulted in only a slight increase in enzyme activity. Enzyme activity in parenchymal cells under similar conditions was increased sixfold and fivefold by 3-methylcholanthrene and ß-naphthoflavone, respectively, but not by phenobarbital.

scholarly journals Intracellular enzymes of collagen biosynthesis in rat liver as a function of age and in hepatic injury induced by dimethylnitrosamine. Purification of rat prolyl hydroxylase and comparison of changes in prolyl hydroxylase activity with changes in immunoreactive prolyl hydroxylase

1976 ◽  
Vol 158 (2) ◽  
pp. 369-376 ◽  
Author(s):  
J Risteli ◽  
L Tuderman ◽  
K I Kivirikko
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Hepatic Injury ◽  
Specific Activity ◽  
Prolyl Hydroxylase ◽  
Newborn Rats ◽  
Hydroxylase Activity ◽  
Immunoreactive Protein ◽  
Molecular Weights ◽  
Polypeptide Chains

Prolyl hydroxylase was purified from newborn rats by affinity chromatography using poly(L-proline), and antiserum to the enzyme was prepared in rabbits. The rat prolyl hydroxylase was similar to the chick and human enzymes with respect to specific activity, molecular weight and molecular weights of the polypeptide chains. The activity of prolyl hydroxylase and the content of immunoreactive enzyme were measured in rat liver as a function of age in experimental hepatic injury. Active prolyl hydroxylase comprised about 13.2% of the total immunoreactive protein in the liver of newborn rats and the value decreased to about 3.6% at the age of 420 days. This decrease was due to a decrease in the enzyme activity, whereas only minor changes were found in the content of the immunoreactive protein. In hepatic injury, a significant increase was found in the ratio of active enzyme to total immunoreactive protein, owing to an increase in the enzyme activity. The data indicate that prolyl hydroxylase activity in rat liver is controlled in part by a mechanism which does not involve changes in the content of the total immunoreactive protein.

Sex-dependent effect of streptozotocin-induced diabetes mellitus on hepatic steroid metabolism in the rat

1986 ◽  
Vol 111 (2) ◽  
pp. 217-221 ◽  
Author(s):  
Paul Skett
Keyword(s):  
Diabetes Mellitus ◽  
Sex Differences ◽  
Drug Metabolism ◽  
Rat Liver ◽  
Steroid Metabolism ◽  
Hydroxylase Activity ◽  
Dependent Effect ◽  
Maintenance Of Sex ◽  
Streptozotocin Induced Diabetes

Abstract. Diabetes mellitus is known to affect drug and steroid metabolism in the rat liver. Recently it has been shown that the effect on drug metabolism is both transient and sex-dependent. This study shows that the effect of diabetes on steroid metabolism is also sex-dependent i.e. only seen in the male and the effect is always to abolish the sex differences in steroid metabolism found in the intact animals. 7α-hydroxylase activity, which is higher in the female, is increased by diabetes in the male whereas 6β-hydroxylase, 16α-hydroxylase and 17-oxosteroid reductase, which are all higher in the male, are decreased by diabetes. This is a very similar result to that found for drug metabolism and indicates that insulin plays a role in the maintenance of sex differences in hepatic steroid metabolism in the rat as it does for drug metabolism.

scholarly journals Uridine kinase in embryonic rat liver. Modulation of enzyme activity by 5-azacytidine

1973 ◽  
Vol 133 (4) ◽  
pp. 609-613 ◽  
Author(s):  
J. Veselý ◽  
A. Čihák
Keyword(s):  
Enzyme Activity ◽  
Postnatal Development ◽  
Rat Liver ◽  
Kinase Activity ◽  
Liver Enzymes ◽  
Adult Rats ◽  
Uridine Kinase

Uridine kinase activity in rat liver decreases during embryonic and postnatal development. Administration of 5-azacytidine enhances liver uridine kinase activity in adult rats, but depresses it in embryos. The liver enzymes from the foetus and the adult are precipitated at different (NH4)2SO4 concentrations although they are eluted at about the same position on chromatography on a column of Sepharose 6B.

Distribution and induction of aflatoxin B1-9a-hydroxylase activity in rat liver parenchymal and non-parenchymal cells

1996 ◽  
Vol 70 (9) ◽  
pp. 553-558 ◽  
Author(s):  
M. Gemechu-Hatewu ◽  
K. -L. Platt ◽  
F. Oesch ◽  
P. Steinberg
Keyword(s):  
Rat Liver ◽  
Aflatoxin B1 ◽  
Hydroxylase Activity ◽  
Liver Parenchymal ◽  
Parenchymal Cells

Influence of amino acids on rat liver phenylalanine hydroxylase activity

1964 ◽  
Vol 206 (2) ◽  
pp. 341-344 ◽  
Author(s):  
R. A. Freedland ◽  
M. C. Krakowski ◽  
Harry A. Waisman
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Phenylalanine Hydroxylase ◽  
Marked Decrease ◽  
Hydroxylase Activity ◽  
Short Term ◽  
Ad Libitum

The influence of oral and of injected amino acids on rat liver phenylalanine hydroxylase activity has been studied in both short-term and extended experiments. Phenylalanine added to the diet in moderate amounts ordinarily causes an increase in enzyme activity, but when excess phenylalanine was included in the diet, it caused a marked decrease in the enzyme activity in rats fed ad libitum. Tryptophan or tyrosine added to the diet in the absence of added phenylalanine increased the enzyme activity in these rats. Excess tryptophan, but not tyrosine, could counteract the effect of phenylalanine on this enzyme after an 18-hr fast. There were dramatic differences in phenylalanine hydroxylase activity when various amino acids were injected. Injection of tryptophan or glycine decreased the phenylalanine hydroxylase activity in rat liver. Injections of other amino acids, notably phenylalanine and tyrosine, had no effect on the phenylalanine hydroxylase activity 5 hr after injection.

Effect of age, sex, and nutrition on liver phenylalanine hydroxylase activity in rats

1962 ◽  
Vol 202 (1) ◽  
pp. 145-148 ◽  
Author(s):  
R. A. Freedland ◽  
M. C. Krakowski ◽  
Harry A. Waisman
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Phenylalanine Hydroxylase ◽  
Total Amino Acid ◽  
Rapid Decline ◽  
Female Rat ◽  
Hydroxylase Activity ◽  
Adult Age ◽  
Number Of Factors ◽  
Amino Acid Intake

This study provides data on a number of factors that influence phenylalanine hydroxylase activity in rat liver. By means of a method which utilizes crude liver homogenates, the enzyme activity was determined in rat liver obtained from early embryos to 150-day-old animals. The activity increases with age to a maximum at the young adult age of 50–60 days and then declines. The most rapid increase in activity was found between 18–21 days. The female rat livers show a rapid decline in activity with increasing age, then stabilize at a lower activity than males after maturity is reached. Fasting causes a marked drop in activity, and diets deficient in phenylalanine cause a decrease in the enzyme activity. High casein diets, which increase the phenylalanine and total amino acid intake, had no apparent effect on the level of enzyme activity.

GONADAL FACTORS REGULATING THE ACTIVITY OF THE 17β-HYDROXYSTEROID OXIDOREDUCTASE IN RAT LIVER

1974 ◽  
Vol 77 (4) ◽  
pp. 727-736 ◽  
Author(s):  
H. Thaler-Dao ◽  
H. Breuer
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Adult Female ◽  
Female Rats ◽  
Male Rats ◽  
Steroid Metabolism ◽  
Normal Male ◽  
Normal Female ◽  
Cytosol Fraction ◽  
Key Enzyme

ABSTRACT The activity of the 17β-hydroxysteroid oxidoreductase (17β-HSOR), catalysing the oxidoreduction of oestradiol-17β and oestrone, has been studied in the cytosol fraction of rat liver under various conditions. The activity of the enzyme increased during maturation and reached a plateau at 100 days in females and at 180 days in males. In adult male rats, the activity of the 17β-HSOR was about 60% higher than in adult female rats. When female animals were castrated, the development of enzyme activity was similar to that observed in male rats; there was no difference in enzyme activity between adult castrated female rats and normal male rats. In normal female rats the activity of the 17β-HSOR was high during metoestrus and dioestrus, and low during pro-oestrus and oestrus. These findings show that oestrogens have a repressing effect on the activity of a key enzyme of steroid metabolism in rat liver.

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