Search PubMed⌕ Search

Biomedical subjects

R Beitner

Publications and source records attributed to R Beitner.

At least 55 records · Page 3Linked to original sources
PubMed1985

Trifluoperazine abolishes the actions of bradykinin on glucose 1,6-bisphosphate levels and on the activities of glucose 1,6-bisphosphatase, phosphofructokinase and phosphoglucomutase.

Injection of trifluoperazine abolished the bradykinin-induced decrease in intracellular concentration of glucose 1,6-bisphosphate (Glc-1,6-P2) in rat tibialis anterior muscle and skin. These changes in Glc-1,6-P2 levels may be attributed to the changes in the activity of glucose 1,6-bisphosphatase (the enzyme that degrades Glc-1,6-P2), which was markedly enhanced by bradykinin and reversed by trifluoperazine. Concomitantly to the changes in Glc-1,6-P2, the potent activator of phosphofructokinase and phosphoglucomutase, the activities of these enzymes were reduced by bradykinin and restored by trifluoperazine. These findings suggest that trifluoperazine treatment may have a beneficial effect on the depressed glycolysis induced by bradykinin in tissue damage.

Animals↗
PubMed1984

Opposite changes with age in liver and muscle in the mitochondrial and soluble glucose-1,6-bisphosphate and 6-phosphogluconate dehydrogenase.

Glucose-1,6-bisphosphate (Glc-1,6-P2), the powerful regulator of carbohydrate metabolism, was markedly decreased in liver of adult rats (2 months of age) as compared to young rats (1-2 weeks of age). This regulator was found to be present in both the mitochondrial and soluble fractions of liver. Its concentration in both these fractions was decreased with age. Concomitant to the decrease in Glc-1,6-P2, which is a potent inhibitor of 6-phosphogluconate dehydrogenase, the activity of this enzyme was markedly increased with age in both the mitochondrial and soluble fractions. However, the increase in this enzyme's activity was more pronounced in the mitochondrial fraction. The mitochondrial enzyme was more susceptible to inhibition by Glc-1,6-P2 as compared to the soluble enzyme, and this may explain the greater enhancement in its activity with age in this fraction. The tibialis anterior muscle exhibited changes with age opposite to those found in liver; Glc-1,6-P2 concentration, in both the mitochondrial and soluble fractions of muscle increased with age, and this increase was accompanied by a concomitant reduction in the activity of the mitochondrial and soluble 6-phosphogluconate dehydrogenase. Similar to liver, the mitochondrial enzyme was more affected by age, as it also exhibited a greater susceptibility to inhibition by Glc-1,6-P2.

Aging↗
PubMed1984

Increase in glucose 1,6-bisphosphate levels, activation of phosphofructokinase and phosphoglucomutase, and inhibition of glucose 1,6-bisphosphatase in muscle induced by trifluoperazine.

Injection of trifluoperazine (TFP) to rats induced a significant rise in the level of glucose 1,6-bisphosphate (Glc-1,6-P2) in muscle. This increase in Glc-1,6-P2, the potent activator of phosphofructokinase and phosphoglucomutase, was accompanied by a marked activation of both enzymes, when assayed in the absence of exogenous Glc-1,6-P2 under conditions in which these enzymes are sensitive to regulation by endogenous Glc-1,6-P2. Glucose-1,6-bisphosphatase (the enzyme that degrades Glc-1,6-P2) was markedly inhibited following the injection of TFP, which may account for the rise in the Glc-1,6-P2 level. Previous results from this laboratory have revealed that muscle damage or weakness is characterized by a decrease in Glc-1,6-P2 levels, leading to a marked reduction in the activities of phosphoglucomutase and phosphofructokinase (the rate-limiting enzyme in glycolysis). The present results suggest that TFP treatment may have a beneficial effect on the depressed glycolysis in muscle weakness or damage.

Animals↗
PubMed1984

Inhibition of mitochondrial and soluble hexokinase from various rat tissues by glucose 1,6-bisphosphate.

Mitochondrial and soluble Type I and Type II hexokinase from various rat tissues differed in their susceptibility to inhibition by glucose-1,6-bisphosphate (Glc-1,6-P2). In tissues where Type I is the predominant form, the mitochondrial enzyme was less susceptible to inhibition by Glc-1,6-P2 than the soluble enzyme, especially at high Mg2+ concentration. In tissues where Type II is the predominant form, the mitochondrial enzyme was more susceptible to inhibition by Glc-1,6-P2 than the soluble enzyme, especially at low Mg2+ concentration. The results suggest that changes in the intracellular concentrations of Glc-1,6-P2 and Mg2+ under various conditions would affect the activity of the bound and soluble hexokinase from different tissues in a different manner.

Adipose Tissue↗
PubMed1984

Influence of bradykinin on glucose 1,6-bisphosphate and cyclic GMP levels and on the activities of glucose 1,6-bisphosphatase, phosphofructokinase and phosphoglucomutase in muscle.

The intracellular concentration of glucose-1,6-bisphosphate (Glc-1,6-P2) in rat tibialis anterior muscle was markedly decreased following the injection of bradykinin. Injection of bradykinin also induced a significant increase in the level of cyclic GMP in muscle. The activity of glucose-1,6-bisphosphatase, the enzyme that degrades Glc-1,6-P2, was markedly enhanced by bradykinin, which may account for the decrease in the level of Glc-1,6-P2. The decrease in Glc-1,6-P2, the potent activator of phosphofructokinase and phosphoglucomutase, was accompanied by a concomitant reduction in these enzymes' activities. The bradykinin-induced decrease in Glc-1,6-P2 and in the activity of phosphofructokinase, the rate-limiting enzyme in glycolysis, may be involved in the pathogenic influences of this hormone in various clinical conditions.

Animals↗
PubMed1983

Age-dependent changes in glucose 1,6-bisphosphate levels and in the activities of glucose 1,6-bisphosphatase, and particulate hexokinase and 6-phosphogluconate dehydrogenase in rat skin.

The levels of glucose 1,6-bisphosphate (Glc-1,6-P2), the powerful regulator of carbohydrate metabolism, changed in rat skin during growth: Glc-1,6-P2 increased during the first week of age, and thereafter was dramatically reduced during maturation. The activity of glucose 1,6-bisphosphatase, the enzyme that degradates Glc-1,6-P2, changed with age in an invert manner as compared to the changes in Glc-1,6-P2. These findings suggest that the age dependent changes in this enzyme's activity may account for the changes in intracellular Glc-1,6-P2 concentration. The age-related changes in Glc-1,6-P2 were accompanied by concomitant changes in the activities of particulate (mitochondrial) hexokinase and 6-phosphogluconate dehydrogenase, the two enzymes known to be inhibited by Glc-1,6-P2. The activities of both these enzymes in the soluble fraction were not changed with age. The particulate enzymes were more susceptible to inhibition by Glc-1,6-P2 than the soluble activities, which may explain why only the particulate, but not the soluble activities, correlated with the age-dependent changes in tissue Glc-1,6-P2. These results suggest that the changes in particulate hexokinase and 6-phosphogluconate dehydrogenase resulted from changes in intracellular concentration of Glc-1,6-P2. The marked reduction in Glc-1,6-P2 during maturation, accompanied by activation of mitochondrial hexokinase and 6-phosphogluconate dehydrogenase, may reflect an enhancement in skin metabolism during growth.

Aging↗
PubMed1983

Changes in the levels of glucose 1,6-diphosphate and cyclic GMP, and in the activities of phosphofructokinase and phosphoglucomutase induced by serotonin in muscle.

Injection of serotonin (5-hydroxytryptamine) induced a marked decrease in the level of glucose 1,6-diphosphate (Glc-1,6-P2) in the rat tibialis anterior muscle. Concomitant to the decrease in Glc-1,6-P2, the potent activator of phosphofructokinase and phosphoglucomutase, the activities of both these enzymes were markedly reduced by serotonin. The level of Glc-1,6-P2 and the activities of phosphofructokinase and phosphoglucomutase increased with age in the tibialis anterior muscle and the effect of serotonin was more pronounced in the older animals. Serotonin also induced a significant increase in the level of cyclic GMP in muscle. The serotonin-induced changes in the normal muscle mimic the changes in carbohydrate metabolism we found previously in muscular dystrophy.

Animals↗
PubMed1982

Effects of lithium on the activities of phosphofructokinase and phosphoglucomutase and on glucose-1,6-diphosphate levels in rat muscles, brain and liver.

Incubation of rat diaphragm muscle in the presence of lithium chloride (a drug used widely in the therapy of patients with mental illness), resulted in a sharp decrease in the level of glucose-1,6-diphosphate (Glc-1,6-P2), the powerful regulator of carbohydrate metabolism. This decrease in Glc-1,6-P2, the most potent activator of phosphofructokinase and phosphoglucomutase, was accompanied by a marked reduction in the activities of both enzymes, when assayed in the absence of exogenous Glc-1,6-P2 under conditions in which these enzymes are sensitive to regulation by endogenous Glc-1,6-P2. A decrease in Glc-1,6-P2 and the concomitant reduction in the activities of phosphofructokinase and phosphoglucomutase, were also obtained in the rat gastrocnemius and tibialis anterior muscles, as well as in brain, following Li+ injection. In contrast to its effects in muscles and brain, Li+ did not exert any effect on Glc-1,6-P2 level and on the enzymes' activities in the liver. The marked inhibition of brain and muscles phosphofructokinase (the rate-limiting enzyme in glycolysis) induced by Li+, may play an important role in the mechanism of the therapeutic action of this agent in the manic state.

Animals↗
PubMed1982

The participation of glucose-1,6-diphosphate in the regulation of hexokinase and phosphoglucomutase activities in brains of young and adult rats.

1. The level of glucose-1,6-diphosphate (Glc-1,6-P2), the powerful regulator of carbohydrate metabolism, was found to be strikingly decreased in brains of adult rats (5 months of age) as compared to young (10-14 days of age). 2. This age-related decrease in Glc-1,6-P2, the potent inhibitor of hexokinase and activator of phosphoglucomutase, was accompanied by a correlated increase in the activity of hexokinase and a reduction in phosphoglucomutase. 3. Evidence is provided showing that Glc-1,6-P2 participates in the regulation of these enzymes' activities with age. 4. The age-related changes in Glc-1,6-P2 and in the enzymes' activities in brain were opposite to those which we previously found in skeletal muscle. 5. These results suggest that Glc-1,6-P2 is involved in the regulation of carbohydrate metabolism during growth in both brain and muscle, as well as in the interrelationship between these two tissues.

Adenosine Triphosphate↗
PubMed1979

Inhibition of 6-phosphogluconate dehydrogenase (decarboxylating) by glucose 1,6-bisphosphate.

Glucose 1,6-bisphosphate, the powerful common regulator of several key enzymes in carbohydrate metabolism, was found to exert a potent inhibitory effect on the activity of 6-phosphogluconate dehydrogenase (decarboxylating) from yeast and several rat tissues. These findings suggest that glucose 1,6-bisphosphate may have a regulatory influence on the pentose phosphate pathway.

Animals↗