Plasma esterase activities in rats fed magnesium-deficient diets

In a study with rats it was determined whether dietary magnesium concentration affects plasma esterase activities. The feeding of a diet with 0.01% (w/w) instead of 0.04% magnesium reduced plasma magnesium concentration by 50%. Plasma total esterase, arylesterase and butyrylcholinesterase activities were significantly decreased in the magnesium-deficient rats. In rats fed a diet containing 0.02% magnesium, plasma magnesium concentration was lowered by 30%, and group mean plasma total esterase activity was decreased, but not the activities of arylesterase and butyrylcholinesterase.     

Activities of ornithine aminotransferase and ornithine decarboxylase in chronically uremic rats

The activities of two enzymes mediating different pathways of ornithine catabolism were measured in liver and kidney of chronically uremic rats and their pair-fed controls. Two months following partial nephrectomy hepatic ornithine aminotransferase (OAT) activity tended to be lower in uremic rats and was correlated with urea clearance and with carbamoyl phosphate synthetase activity. Renal OAT activity in uremic rats was also correlated with urea clearance. When uremic rats were maintained for five months, OAT activity was significantly decreased in liver but not in kidney and the activity of ornithine decarboxylase (ODC), the enzyme regulating polyamine biosynthesis, was reduced in both liver and kidney. In cross-over experiments, evidence was obtained for a factor in uremic kidney cytosol which inhibited renal ODC activity.     

Activities of arginine and ornithine decarboxylases in various plant species

In extracts from the youngest leaves of Avena sativa, Hordeum vulgare, Zea Mays, Pisum sativum, Phaseolus vulgaris, Lactuca sativa, and four pyrrolizidine alkaloid-bearing species of Heliotropium, the activities of ornithine decarboxylase, close to V_max, ranged between traces and 1.5 nanomoles per hour per gram fresh weight when based on putrescine formed during incubation with labeled ornithine. The arginine decarboxylase activities in the same extracts ranged between 8 and 8000 nanomoles per hour per gram fresh weight being lowest in the borages and highest in oat and barley. α-Difluoromethylornithine and α-difluoromethylarginine inhibited ornithine and arginine decarboxylases, respectively, in all species. Agmatine, putrescine, spermidine, and spermine were found in all, diaminopropane in eight, and cadaverine in three species.

No correlation was observed between arginine or ornithine decarboxylase level and the levels of total polyamines. The in vitro decarboxylase activities found in the borages cannot explain the high accumulation of putrescine-derived pyrrolizidines in their youngest leaves if the pyrrolizidines are produced in situ from arginine and/or ornithine as precursors; other possibilities are discussed.

In assays of ornithine decarboxylase, an interference of decarboxylation not due to this enzyme was observed in extracts from all species. In arginine decarboxylase assays, the interfering decarboxylation as well as the interference of arginase were apparent in two species. Addition of aminoguanidine was needed to suppress oxidative degradation of putrescine and agmatine during incubation of extracts from pea, bean, lettuce, Heliotropium angiospermum, and Heliotropium indicum.

     

Mineral metabolism of rats fed various levels of aluminum hydroxide

Biological Trace Element Research - The effect of ingesting nutritionally complete diets with added aluminum hydroxide (257 μg Al/g diet in study A and 1075 μg Al/g diet in study B) was...     

Monoamine and diamine oxidase activities in uremic rats

The activities of monoamine and diamine oxidases in various organs and tissues and the amine levels in plasma and urine were determined in chronically uremic and pair-fed control rats. Plasma amine levels were elevated in uremic animals while the urinary excretion of amines was decreased. In uremic as compared to control animals, monomaine oxidase activity was decreased in kidney and muscle, increased in heart and plasma and not altered in liver and cerebrum. Diamine oxidase activity in uremic rats was decreased in kidney, increased in plasma and unchanged in liver and muscle. These alterations of amine oxidase activities in renal failure may affect the metabolism of many amines and thus contribute to the pathogenesis of the uremic syndrome.     

Lipoprotein lipase and lipogenic enzyme activities in adipose tissue from rats fed different lipid sources

This work was designed to study the effect of different lipid sources on the activities of lipoprotein lipase and lipogenic enzymes in adipose tissue from rats fedad libitum or energy-controlled diets. Male Wistar rats were fed diets containing 40% of energy as fat (olive oil, sunflower oil, palm oil or beef tallow), for 4 wk. Underad libitum feeding no differences were found among dietary fat groups in final body weight, adipose tissue weights and total body fat. Under energy-controlled feeding, despite isoenergetic intake, rats fed the beef tallow diet gained significantly less weight than rats fed the other three diets. Beef tallow fed rats showed the lowest values for adipose tissue weights and total body fat. When rats had free access to food no effect of dietary lipid source on lipogenic enzyme activities was found. In contrast, under energy-controlled feeding rats fed the beef tallow diet showed significantly higher activities of glucose-6-phosphate dehydrogenase and fatty acid synthase than rats fed the other three diets. Heparin-releasable lipoprotein lipase activity in perirenal and subcutaneous adipose tissues was not different among rats fed olive oil, safflower oil, palm oil or beef tallow. When comparing both adipose tissue anatomical locations, significantly higher activities were found in subcutaneous than in perirenal fat pad independently of dietary fat. In conclusion, under our experimental protocol, lipogenesis in rat adipose tissue does not seem to be affected by dietary fat type.     

Effects of ornithine or arginine administration on serum amino acid levels

In healthy humans after overnight fasting, an oral administration of ornithine induced a new steady state: an accumulation of serum alanine and proline, a decrease in serum valine concentration, transient reductions in serum urea and urinary urea contents, and then an increased urea excretion. On the other hand, an oral administration of arginine resulted in an anabolic state: decreases in serum leucine and isoleucine concentrations, reductions in serum glucose and free fatty acid contents and a rapid increase in serum insulin level. It was assumed that the effect of ornithine administration may be exerted through an activation of hepatic System A transport and that of arginine is an insulin-mediated action.     

Neurotoxin 6-aminonicotinamide affects levels of soluble proteins and enzyme activities in various tissues of golden hamsters

The effects of neurotoxin 6-aminonicotinamide (6-AN) on the levels of soluble proteins and enzyme activities in various tissues of golden hamsters were investigated. SDS-polyacrylamide gel electrophoresis showed that a soluble spinal cord protein with molecular mass 75.0 kDa was present at a higher concentration in the treated group compared to that in the control while that of a molecular mass 64.8 kDa appeared to be missing. However, there were no noticeable differences in protein concentrations observed with the cerebrum, brain stem, and cerebellum. Similarly, treatment with 6-AN decreased the concentration of a soluble protein in pectoral muscle having molecular mass 97.2 kDa and increased those having molecular masses 207.4 and 32.1 kDa. In the kidney, soluble proteins with molecular masses 176.6 kDa was missing and those of molecular masses 97.6, 49, 43.3, and 33.8 kDa were decreased whereas those of molecular masses 64.7 and 33.1 kDa were increased. In the testis the soluble proteins with molecular masses 125.4, 88.7, 69.0, 31.2, 19.1, and 17.4 kDa were missing and those of molecular masses 97.0, 51.3, 42.0, 33.0, 27.2, and 22.6 kDa were present in lower amounts whereas those of molecular masses 311.5, 75.0, 64.0, 54.1, and 53.2 kDa were present in higher amounts. The specific activity of 6-phosphogluconate dehydrogenase was markedly increased in the liver but that of other tissues was not affected. Acetylcholinesterase activity was markedly reduced in the spleen but was enhanced in the intestine. Monoamine oxidase activity was markedly reduced in the brain stem, cerebrum, kidney, and liver. The results suggest that the changes in levels of soluble proteins and enzyme activities shown with golden hamster tissues by 6-AN administration were quite different from those shown with quail tissues.     

Diurnal levels of polyamines and activities of ornithine andS-adenosyl-l-methionine decarboxylases in mouse brain

The levels of putrescine and spermine in mouse brain were rather constant at different times of day, as were the activities of ornithine andS-adenosyl-l-methionine decarboxylases. Contrary to an earlier report, the level of spermidine was found to be relatively constant. A possibly significant feature in the present results was the steady decline during the light period and rise during darkness of cerebral spermidine and spermine levels, the differences between maximum and minimum being about 15% for both compounds.     

Effects of 6-aminonicotinamide on levels of soluble proteins and enzyme activities in various tissues of Japanese quail

The effects of 6-aminonicotinamide (6-AN) on the levels of soluble proteins and enzyme activities in various tissues of Japanese quail were investigated. SDS-polyacrylamide gel electrophoresis showed that the soluble proteins with molecular masses corresponding to 160.4 and 52.5 kDa were either missing or present at lower concentrations in the brain of the 6-AN treated group compared to those in the control group. The soluble liver proteins with molecular masses 200, 120 and 70.5 kDa were missing in the treated group compared to those in the control while those of a molecular mass 15.1 kDa were found to be present at higher concentrations. Similarly, treatment with 6-AN decreased the concentration of soluble proteins in pectoral muscle with molecular masses 92.3, 54.5, 43.5, 41.2, 34.5, 27.5, 20.1 and 17.5 kDa and increased those with molecular masses 96.5, 37.7, 25.0, 19.3, 16.6, 13.8 and 10.8 kDa. In the heart, soluble proteins with molecular mass 84.6 kDa were increased. There was a marked reduction in the treatment group in the concentration of NAD in pectoral muscle but not in other tissues. A similar observation was also made with total RNA levels. The specific activity of malic enzyme was markedly increased by 6-AN treatment in the kidney and pectoral muscle but reduced in the liver. 6-Phosphogluconate dehydrogenase and lactate dehydrogenase activities were markedly reduced in the liver. Glyceraldehyde-3-phosphate dehydrogenase activity was significantly decreased in liver and pectoral muscle. NAD glycohydrolase activity was markedly decreased in pectoral muscle. Acetylcholinesterase activity was markedly reduced in liver but was enhanced in pectoral muscle. The results suggest that the metabolic actions of 6-AN are specific for certain proteins in the liver and muscle with the effect being most pronounced in muscle. The effects are also quite distinct from those shown by its analogue 3-acetylpyridine.     

Effect of arginine,ornithine and citrulline supplementation upon performance and metabolism of trained rats

During intense exercise there is an augmented production of ammonia and IMP in the exercised muscle that could be related to the establishment of peripheral fatigue. In order to prevent this accumulation, the urea cycle in the liver eliminates ammonia in the form of urea and the skeletal muscle buffers the increase of ammonia via transamination reactions. In the present study we evaluated the effect of arginine, citrulline and ornithine supplementation, intermediates of the urea cycle, on the performance of sedentary and swimming-trained rats submitted to a single bout of exhaustive exercise. We also measured the glycogen content of the soleus and gastrocnemius muscles and of the liver, as well as the plasma concentrations of ammonia, urea, glutamine, glucose and lactate. The results indicate that arginine, citrulline and ornithine supplementation increased the flux of substrate through the reaction catalysed by glutamine synthetase, leading to increased glutamine production after an exhaustive bout of exercise, and of the mechanism involved in ammonia buffering.     

Behavior of various enzyme activities during high blood lactate and pyruvate levels in albino rats reared in a normobaric hypoxic atmosphere for 1 or 2 generations

Albino rats Wistar family raised in normobaric hypoxic environment (10% O2 in N2) since one or two generations showed an increase in arterial blood creatine-kinase, glutamate-dehydrogenase, lactic-dehydrogenase, lactate and pyruvate when compared with normoxic controls. Moreover the values found in hypoxic rats of second generation were intermediate between those found in hypoxic rats of first generation and normoxic controls. These differences are probably due to an improved efficiency of the processes of cellular adaptation to the hypoxic environment when named species remain in hypoxic environment for more than one generation.