Ascorbic acid biosynthesis in the mammalian kidney

Summary The egg-laying mammals (Prototheria) synthesize L-ascorbic acid only inkidney, as is characteristic of reptiles. Bandicoots (Marsupialia) synthesize it in both kidney and liver. 2 other species of marsupials (kangaroos) synthesize it primairly in liver, but some individuals also synthesize in kidney.This study was supported by NSF grant INT77-15934; the Carnegie Museum of Natural History provided one field assistant. We thank M. Birney, D. Dellow, K. Jenness, and L. Robbins for field assistance, A. G. Lyne for providing the live bandicoots, and the New South Wales National Parks and Wildlife Service for issuance of collecting permits (SLF52 and SLF84).     

Interaction of mitochondrial porin with cytosolic proteins.

Intracellular phosphorylation is an important step in active uptake and utilization of carbohydrates. For example glucose and glycerol enter the liver cell along the extra intracellular gradient by facilitated diffusion through specific carriers and are concentrated inside the cell by phosphorylation via hexokinase or glycerol kinase. Depending on the function of the respective tissue the uptake of carbohydrates serves different metabolic purposes. In brain and kidney medulla cells which depend on carbohydrates, glucose and glycerol are taken up according to the energy demand. However, in tissues such as muscle which synthesize glycogen or like liver which additionally produce fat from glucose, the uptake of carbohydrates has to be regulated according to the availability of glucose and glycerol. How the reversible coupling of the kinases to the outer membrane pore and the mitochondrial ATP serves to fulfil these specific requirements will be explained as well as how this regulates the carbohydrate uptake in brain according to the activity of the oxidative phosphorylation and how this allows glucose uptake in liver and muscle to persist in the presence of high glucose 6-phosphate without activating the rate of glycolysis.     

Chronic hydrogen peroxide intake and peroxide metabolizing enzyme activities in some tissues of mice and rats

Chronic daily intake of 0.5% H2O2 in drinking water decreased Se-dependent glutathione peroxidase (Se-GSHPx) activity in rat skeletal muscle, kidney and liver. Non-Se GSHPx activity decreased in kidney. Deprivation of drinking water decreased Se-GSHPx activity in kidney and non-Se GSHPx activity in kidney and liver. H2O2 intake decreased activity of catalase in rat skeletal muscle. H2O2 intake or water deprivation caused no changes in these enzyme activities in mice.     

Interaction of mitochondrial porin with cytosolic proteins

Summary Intracellular phosphorylation is an important step in active uptake and utilization of carbohydrates. For example glucose and glycerol enter the liver, cell along the extra intracellular gradient by facilitated diffusion through specific carriers and are concentrated inside the cell by phosphorylation via hexokinase or glycerol kinase. Depending on the function of the respective tissue the uptake of carbohydrates serves different metabolic purposes. In brain and kidney medulla cells which depend on carbohydrates, glucose and glycerol are taken up according to the energy demand. However, in tissues such as muscle which synthesize glycogen or like liver which additionally produce fat from glucose, the uptake of carbohydrates has to be regulated according to the availability of glucose and glycerol. How the reversible coupling of the kinases to the outer membrane pore and the mitochondrial ATP serves to fulfil these specific requirements will be explained as well as how this regulates the carbohydrate uptake in brain according to the activity of the oxidative phosphorylation and how this allows glucose uptake in liver, and muscle to persist in the presence of high glucose 6-phosphate without activating the rate of glycolysis.     

Extraadrenal adrenaline formation by two separate enzymes

Summary Adrenaline (A) is synthesized in the adrenal medullae by the enzyme phenylethanolamine-N-methyltransferase (PNMT). After surgical removal of the adrenal medullae tissue A levels ranged from 22% of control in the heart to 125% of control in the liver. Use of a novel assay to measure tissue A formation revealed that many tissues can synthesize A using PNMT and another enzyme that N-methylates both noradrenaline and dopamine. These enzymes are non-neuronal, inducible and synthesize a major fraction of tissue and urine A.     

Determination of polyamine oxidase activities in human tissues

A very simple fluorometric assay for polyamine oxidase (PAO) in tissues, with N1-monoacetylspermine as substrate, is described. The PAO was present in all human organs tested; it was highest in the liver, followed by the testis, kidney, spleen and small intestine.     

Extraadrenal adrenaline formation by two separate enzymes

Adrenaline (A) is synthesized in the adrenal medullae by the enzyme phenylethanolamine-N-methyltransferase (PNMT). After surgical removal of the adrenal medullae tissue A levels ranged from 22% of control in the heart to 125% of control in the liver. Use of a novel assay to measure tissue A formation revealed that many tissues can synthesize A using PNMT and another enzyme that N-methylates both noradrenaline and dopamine. These enzymes are non-neuronal, inducible and synthesize a major fraction of tissue and urine A.     

Sorbitol dehydrogenase in Anas platyrhynchos and Zenaida auriculata auriculata during development.

Sorbitol dehydrogenase (E.C.N. 1.1.1.14) was studied in liver, kidney and gonads of Zenaida auriculata auriculata (golden pigeon) and of Anas platyrhynchos (creole domestic duck) from South American faunes. The specific activity of SDH increased from embryonic to adult stage and is higher in the Anas platyrhynchos tissues. The electrophoretic studies performed in liver and kidney of both species during development showed variations in the number and intensity of the bands in accordance with the age and the species.     

Changes in the distribution of gamma-glutamyl transferase in the organs of the mouse as a function of development]

In the Mouse, gamma-glutamyl transferase distribution changes with development in the kidney and the liver; on the contrary, its activity remains almost equal and low in other organs. In the liver, a low activity is observed in the fetus and the new-born up to the 3rd day of life; then it is no more measurable. In the kidney, the low enzyme activity of the fetus is multiplied by 10 in the 10 first days of life and by 50 in the 6 first weeks.     

Calcitonin: effect on protein synthesis in different rat tissues

Protein synthesis was inhibited in the pancreas whereas it was enhanced in the kidney and intestine (jejunum-ileum) after a single injection of porcine calcitonin (20 MRC units/kg b.wt). The incorporation of [3H]leucine into total protein in the brain, heart, liver and stomach did not change after the hormone treatment.     

Determination of polyamine oxidase activities in human tissues

Summary A very simple fluorometric assay for polyamine oxidase (PAO) in tissues, with N¹-monoacetylspermine as substrate, is described. The PAO was present in all human organs tested; it was highest in the liver, followed by the testis, kidney, spleen and small intestine.     

Distribution of polyamine oxidase activity in rat tissues and subcellular fractions

The activity of polyamine oxidase (PAO) in rat tissues, and its subcellular distribution, were assayed using a simple polarographic method. The highest PAO activity was measured in the liver and the lowest in the skeletal muscle. In liver, kidney and uterus the highest specific PAO activity was found in the light mitochondrial fraction. PAO was not found in the microsomal fraction except in the kidney.     

Binding of mercury and zinc to cadmium-binding protein in liver and kidney of goldfish (Carassius auratus L.)

Summary Mercury and zinc, besides Cadmium, are incorporated into cadmium-binding protein found in liver and kidney of goldfish. In the liver, the Cd-BP incorporates more zinc (40%) than in the kidney (1.2%), while mercury show similar affinity for the Cd-BP of this two organs (17 and 12% respectively).Contribution No. 1032 of the Biology Programme, Directorate General XII of the Commission of the European Communities.     

Distribution of polyamine oxidase activity in rat tissues and subcellular fractions.

The activity of polyamine oxidase (PAO) in rat tissues, and its subcellular distribution, were assayed using a simple polarographic method. The highest PAO activity was measured in the liver and the lowest in the skeletal muscle. In liver, kidney and uterus the highest specific PAO activity was found in the light mitochondrial fraction. PAO was not found in the microsomal fraction except in the kidney.     

Comparison in genetically obese and normal rats of the uptake and incorporation of labelled lauric acid, oleic acid, and glycerol by the isolated perfused liver]

Lauric acid, labelled oleic acid and glycerol are perfused in isolated liver of fafa Rats and Wistar Rats previously subjected to fasting. They synthesize TG and PL de novo, though in long time experiments with the normal Rat, the most important method of synthesis is an exchange of AG of the endogenous glycerolipids. However PL are not synthesized with lauric acid. In the livers of fafa Rats the synthesis of TG with oleic acid and glycerol is higher than in livers of Wistar Rats: 16:0 18 : 1 18: 1, 16:0 18: 1 18: 2, 18 : 1 18 :1 18:1, 16 : 0 16 :0 18 : 1 (this TG is not present in liver of Wistar Rat). The hepatic synthesis of PL by the fafa Rat, is less important after 15 min while it is important with Wistar Rats. The synthesized TG with lauric acid (only the TG 12 : 0 12 : 0 12 : 0 with the fafa Rat) are more rapidly oxidized by liver of obese Rat than by liver of normal Rat.     

Chronic hydrogen peroxide intake and peroxide metabolizing enzyme activities in some tissues of mice and rats

Summary Chronic daily intake of 0.5% H₂O₂ in drinking water decreased Se-dependent glutathione peroxidase (Se-GSHPx) activity in rat skeletal muscle, kidney and liver. Non-Se GSHPx activity decreased in kidney. Deprivation of drinking water decreased Se-GSHPx activity in kidney and non-Se GSHPx activity in kidney and liver. H₂O₂ intake decreased activity of catalase in rat skeletal muscle. H₂O₂ intake or water deprivation caused no changes in these enzyme activities in mice.     

Inhibition of cholesterol synthesis ex vivo and in vivo by fluvastatin,a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase

The inhibitory effect of fluvastatin sodium (fluvastatin), a new type of 3-hydroxy-3-methylglutaryl (HMG) coenzyme A inhibitor, on de novo cholesterol synthesis was investigated and compared with that of pravastatin. Fluvastatin at a concentration of 12.5 mg/kg inhibited sterol synthesis ex vivo from [¹⁴C]acetate in rat liver and ileum by 97–99% with respect to the control, while the inhibition in kidney was 55%. The inhibition by fluvastatin in the liver and ileum persisted for approximately 9 h after administration. Significant differences between fluvastatin also had an inhibitory effect on cholesterol synthesis in vivo in various tissues of rats given [¹⁴C]acetate intraperitoneally. Sterol synthesis in the liver, ileum and kidney was inhibited by over 95% 3 h after administration of 6.25 mg/kg of fluvastatin. Significant differences between fluvastatin and pravastatin were found in the liver and ileum. Fluvastatin was more potent than pravastatin in inhibiting both ex vivo and in vivo sterol synthesis in the ileum (but not in kidney) and liver.     

Increase in Na+, K+ -ATPase enzyme units in liver and kidneys from essential fatty acid deficient rats.

(3H)-Ouabain binding to liver and kidney preparations was utilized to estimate the number of Na+, K+-ATPase enzyme units in livers and kidneys from rats fed 2% corn oil supplemented or fat-free diets. The specific (3H)-ouabain binding in liver and kidney preparations from fatty acid deficient rats was increased approximately 40%, but the affinity of the binding sites for ouabain (Kd-value) remained unchanged. The increased concentration of Na+, K+-ATPase enzyme units observed in the essential fatty acid deficient rats may contribute to the reduced body fat accumulation and elevated heat production observed in these animals.     

Effects of Freund's complete adjuvant on the dirunal rhythms of neuroendocrine processes and ornithine decarboxylase activity in various tissues of male rats

The aim of this study was to investigate the effects of Freund's complete adjuvant (FCA) on the diurnal rhythms of hormonal parameters in serum and ornithine decarboxylase (ODC) activity in various tissues of male rats. On days 1–2 after FCA, increase of ODC activity (used to evaluate the level of activation) was observed in the hypothalamus, pituitary gland, adrenal medulla, adrenal cortex, liver and lymphoid tissues, while the ODC activity in the kidney was reduced. This was accompanied by an increase in serum corticosterone. On days 3–4 after FCA, ODC activity remained elevated in the pituitary gland, liver and lymphoid tissues, while the ODC activity in the testes and panceas was reduced; kidney ODC activity returned to baseline. This was associated with increased serum levels of prolactin (Prl) and luteinizing hormone, but decreased growth hormone, testosterone and insulin. The increase in ODC activity in the thymus, as well as the reduced ODC activity in the testes and kidney, can be obtained with paraffin. Furthermore, bromocryptine microcapsules (CBLA) reduced the FCA-induced increase of ODC activity in the pituitary gland, liver and lymphoid tissues (days 3–4) but did not affect the changes in other tissues. The increase in ODC activity in the pituitary gland, liver and lymphoid tissues is specific for FCA. A role for Prl in the induction of ODC in liver and lymphoid tissues is suggested by the fact that CBLA suppresses this enhancement.     

Calcitonin: Effect on protein synthesis in different rat tissues

Summary Protein synthesis was inhibited in the pancreas whereas it was enhanced in the kidney and intestine (jejunumileum) after a single injection of porcine calcitonin (20 MRC units/kg b.wt). The incorporation of [³H]leucine into total protein in the brain, heart, liver and stomach did not change after the hormone treatment.Acknowledgment. This work has been achieved at the Institute of Medical Biochemistry, University of Aarhus, Aarhus, Denmark.