Tissue-specific induction of intestinal glutathione S-transferases by αβ-unsaturated carbonyl compounds

Summary Glutathione S-transferase activity in rat intestinal mucosa was increased by the injection of -unsaturated carbonyl compounds such as phorone and diethylmaleate, but that in the liver and kidney was not. Since the administration of cycloheximide completely blocked the increase of the enzyme activity by phorone, the increase of the activity may be due to de novo synthesis rather than enzyme activation.     

Mitochondrial and cytosolic glutathione after depletion by phorone in isolated hepatocytes

Summary The glutathione content of cytosol and mitochondria of isolated hepatocytes was depleted by addition of a low concentration of phorone (0.5 mM) by 75% and 40% respectively. Different rates of replenishment indicate metabolic separation of cytosolic and mitochondrial glutathione pools. The release from hepatocytes occurred at a rate of about 8 nmol/g wet weight/min, both in controls and after phorone depletion.This work was supported by the Ministerium für Wissenschaft und Forschung. Nordrhein-Westfalen, and by Deutsche Forschungsgemeinschaft.     

Administration of D-alanine did not cause increase of D-amino acid oxidase activity in mice.

D-amino acid oxidase (DAAO) activity was not altered in the liver and kidney by oral administration of D-alanine to adult mice. The enzyme was apparently not induced by the enteric microflora either, since the enzyme activity in the liver and kidney of germ-free mice was not different from that of specific-pathogen-free mice. The times of appearance of DAAO activity and of free D-amino acids in the kidney were elucidated using suckling mice. DAAO activity started to increase 7 days after birth, and reached almost the adult level by 28 days. The content of free neutral D-amino acids also increased with age, in a similar fashion. A possible conclusion is that the enzyme activity normally increases during this period, to eliminate the free D-amino acids which have increased with age in the suckling mice. Consequently, the administration of D-alanine had no further effect in increasing enzyme activity.     

Administration of D-alanine did not cause increase of D-amino acid oxidase activity in mice

D-amino acid oxidase (DAAO) activity was not altered in the liver and kidney by oral administration of D-alanine to adult mice. The enzyme was apparently not induced by the enteric microflora either, since the enzyme activity in the liver and kidney of germ-free mice was not different from that of specific-pathogen-free mice. The times of appearance of DAAO activity and of free D-amino acids in the kidney were elucidated using suckling mice. DAAO activity started to increase 7 days after birth, and reached almost the adult level by 28 days. The content of free neutral D-amino acids also increased with age, in a similar fashion. A possible conclusion is that the enzyme activity normally increases during this period, to eliminate the free D-amino acids which have increased with age in the suckling mice. Consequently, the administration of D-alanine had no further effect in increasing enzyme activity.     

Induction of the synthesis of thymidine kinase by aldosterone in the kidney of the immature male rat

Thymidine kinase activity was studied in kidneys from immature male rats after administration of aldosterone. Kinetic studies showed that the enzyme activity reached its maximum level 24 h after aldosterone injection. That increase was specific for aldosterone and could be related to the synthesis of new molecules of enzyme.     

Induction of the synthesis of thymidine kinase by aldosterone in the kidney of the immature male rat

Summary Thymidine kinase activity was studied in kidneys from immature male rats after administration of aldosterone. Kinetic studies showed that the enzyme activity reached its maximum level 24 h after aldosterone injection. That increase was specific for aldosterone and could be related to the synthesis of new molecules of enzyme.     

Effect of streptozotocin diabetes on adenosine-5′-triphosphate,oxygen consumption and steroidogenesis in testis mitochondria from rats

Summary The activity of the enzyme cleaving the side-chain of cholesterol (rate limiting step in steroidogenesis) was considerably reduced in experimentally induced diabetes. This result was accompained by both an increase in oxygen consumption and an increase in ATP synthesis. Insulin treatment prevented them.     

Evidence of protein kinase activity in 2 murine oncornaviruses]

A protein kinase activity has been detected in two strains of murine Oncornaviruses, MSV/MLV and EFV. This activity phosphorylates not only endogenous viral proteins but also exogenous substrates (histones and phosvitin). The stimulation of enzyme activity by detergents along with the increase of specific activity in viruses treated with trypsin during purification suggest that the enzyme is located in the viral particle.     

Amylase released from the parotid gland by pilocarpine elevates the enzyme activity in the submandibular and sublingual glands of rats

Stimulation by pilocarpine led to a marked increase in amylase activity in the submandibular and sublingual glands and serum, and resulted in a considerable depletion of the enzyme in the parotid gland and pancreas of rats. Parotidectomy reduced these pilocarpine effects. It is concluded that amylase released by pilocarpine from the parotid gland but not from the pancreas elevated the enzyme activity in the submandibular and sublingual glands.     

Trypsin activity in the hepatopancreas ofMacrobrachium lamarrei (Crustacea: Decapoda)

Summary Trypsin from the hepatopancreas ofMacrobrachium lamarrei showed optimum activity at pH 7.5 and temperature 45°C. The enzyme activity increased with the increase in incubation period and enzyme concentration. Michaelis constant of the enzyme was 2.38×10^–2 M.Acknowledgments. The authors are thankful to University Grants Commission, India for the award of a Junior Research Fellowship.     

Glutathione-related enzyme activities in pregnant rat liver

The levels of GSH-related enzyme activities during pregnancy were determined. A significant increase in Selenium-dependent GSH peroxidase and GSH S-transferase E activity was observed. A concomitant increase in gamma-glutamylcysteine synthetase was measured, which indicated an increased ability to synthesize the tripeptide.     

Cell cycle patterns of thymidylate synthetase and 5,10-methylenetetrahydrofolate polyglutamates in cultured mouse hepatoma cells

Summary The regulation of thymidylate synthetase activity was investigated throughout the first cell cycle after release from an isoleucine block in synchronous cultures of mouse hepatoma (Hepa) cells. Activity in cell extracts increased with the onset of S phase and the increased activity was attributed to a parallel increase in enzyme concentration as determined by titration with tritiated fluorodeoxyuridylate. The polyglutamate chain length of reduced folate cofactors, which could also influence thymidylate synthetase activity, was unchanged.Acknowledgments. Supported by grant CA 22754, awarded by the National Cancer Institute, DHEW.     

Relationship between the pentose phosphate shunt and methemoglobin reductase activity in human erythrocytes: Effect of aging on methemoglobin reductase activity.

The increase in methemoglobin reductase activity in human erythrocytes upon incubation with inosine, phosphate, pyruvate occurs only in the presence of methylene blue. No difference in activity of the methemoglobin reductases was observed between enzyme extracts of fresh cells and aged cells.     

Relationship between the pentose phosphate shunt and methemoglobin reductase activity in human erythrocytes: Effect of aging on methemoglobin reductase activity

Summary The increase in methemoglobin reductase activity in human erythrocytes upon incubation with inosine, phosphate, pyruvate occurs only in the presence of methylene blue. No difference in activity of the methemoglobin reductases was observed between enzyme extracts of fresh cells and aged cells.     

Chymotrypsin gene expression during the intermolt cycle in the shrimpPenaeus vannamei (Crustacea; Decapoda)

InPenaeus vannamei, chymotrypsin is present as two isoenzymes in the hepatopancreas. The enzyme has been localized in F-cells by immunocytochemistry using a specific antibody. By in situ hybridization, with a 510 pb cDNA probe encoding for the first 170 amino acids of the shrimp chymotrypsin, mRNA was localized in the same cells. Gene expression was followed during the intermolt cycle by measuring changes in specific activity in crude extracts, and by the estimation of mRNA levels by Northern blots using the same probe. The increase in specific activity in premolt is preceded in early premolt by an increase in the amount of chymotrypsin mRNA. A second increase is observed in postmolt, suggesting a different mode of regulation of gene expression.     

Debriding ability of a novel multi-enzyme preparation isolated from Antarctic krill (Euphausia superba)

Summary The wound-debriding activity of various types of proteolytic enzymes and proteases from Antarctic krill (multi-enzyme system consisting of both endo- and exopeptidases) was evaluated. The results, based on the enzymatically acieved weight reduction of a necrotic animal material (excised rat skin) in vitro, clearly showed that the multi-enzyme system (krill) had a higher degrading activity than the single enzyme preparation, or that with only a few enzymes. The debriding effect of the krill enzymes was markedly related to the enzyme concentration, resulting in 70–100% substrate degradation after 24 h. The digesting capacity of trypsin reached about 50%, but an increase in concentration of this enzyme did not substantially influence its overall activity. The effect of streptokinase-streptodornase, collagenase and plasmin-desoxyribonuclease was weak (10–20% digested).     

Effect of exercise on ribonuclease activity in rat skeletal muscle.

Distribution of ribonuclease activity (measured at pH 7.6) in subcellular fractions of homogenates of rat skeletal muscle was investigated in sedentary animals and after 8 weeks running program. Training increased ribonuclease activity (expressed as units of enzyme per g of muscle protein). There was no increase in nuclear fraction, but in both cytoplasmic and mitochondrial fractions the RNA-ase activity increased 42% and 45% respectively.     

Effect of aldosterone and methylprednisolone on cardiac NaK-ATPase.

Aldosterone (15 microgram BID) and methylprednisolone (8 mg QD) administration to female guinea-pigs augmented both the total and the specific activity of NaK-ATPase but not the activity of adenylate cyclase in the cardiac sarcolemma. The rise in NaK-ATPase was due to increase in the number of enzyme molecules; catalytic activity and ouabain-sensitivity of individual molecules did not change.     

Effect of hormones and cyclic AMP on γ-glutamyltranspeptidase activity of rat mammary gland explants

Summary -Glutamyl transpeptidase activity was assayed in midpregnant rat mammary gland explants at 14, 22 and 38 h, in the presence and absence of insulin, prolactin and corticosterone. With these 3 hormones the explants attained the characteristics of a secretory gland after 22 h of tissue culture, at which time the enzyme exhibited its maximal activity. The addition of dibutyryl cyclic AMP in the presence of the 3 hormones produced a significant increase in enzyme activity, which was maximal with a 1 mM concentration of the cyclic nucleotide. A similar effect was observed when theophylline or theophylline plus dibutyryl cyclic AMP were added to the culture medium.This work was supported by grant B1138-8333 from the Departamento de Desarrollo de la Investigación, Universidad de Chile.     

Carbon tetrachloride modulates the rat hepatic microsomal UDP-glucuronyl transferase activity and membrane fluidity

Summary Modulations in rat hepatic microsomal UDP-glucuronyl transferase activity have been observed during carbon tetrachloride (CCl₄) poisoning, with a large decrease in the enzyme cooperativity and increase in the membrane fluidity, occurring 30 min after administration. The results strengthen the possibility that an increase in microsomal membrane fluidity may be an early key event in liver injury induced by CCl₄.Acknowledgments. This work was supported by funds of the University of Athens.