Effect of cyclic guanosine monophosphate on certain indices of muscle tissue carbohydrate metabolism during the wound process

The effect of intraperitoneal administration of cGMP (0.5 mg per animal) on carbohydrate metabolism of wound area muscle tissue was studied in experiments on rats with linear skin wounds. The content of glycogen, gluconeogenesis, activity of glycogen phosphorylase, lactate dehydrogenase and malate dehydrogenase were studied. Cyclic GMP induced a substantial activation of glycogen metabolism (elevation of gluconeogenesis, increase in the activity of glycogen phosphorylase) even the third day after the operation. The animals not given cGMP demonstrated such an activation only the fifth day following the operation. Under the effect of cGMP the activity of lactate dehydrogenase rose the third day after the operation. Thus cGMP administration to the animals with wounds leads to an earlier mobilization of energy resources thereby promoting the acceleration of wound healing.     

On the activities of glycogen phosphorylase and glycogen synthase in the liver of the rat

A procedure was developed for determination of glycogen synthase and phosphorylase activities in liver after various in vivo physiological treatments. Liver samples were obtained from anaesthetised rats by freeze-clamping in situ. Other procedures were shown to stimulate the activity of phosphorylase and depress the activity of glycogen in the liver. The direction of glycogen metabolism appears to be regulated by the relative proportions of the two enzymes, as shown by a strong positive correlation between total activities and active forms of phosphorylase and synthase. The enzyme activities responded as expected to stimuli such as insulin and glucose, which depressed phosphorylase and increased synthase activity, and glucagon, which increased phosphorylase and decreased synthase activity. In fasted animals approximately 50% of each enzyme was in the active form, which suggests the existence of a potential futile cycle for glycogen metabolism. The role for such a cycle in the regulation of glycogen synthesis and degradation is discussed.     

On the activities of glycogen phosphorylase and glycogen synthase in the liver of the rat.

A procedure was developed for determination of glycogen synthase and phosphorylase activities in liver after various in vivo physiological treatments. Liver samples were obtained from anaesthetised rats by freeze-clamping in situ. Other procedures were shown to stimulate the activity of phosphorylase and depress the activity of glycogen in the liver. The direction of glycogen metabolism appears to be regulated by the relative proportions of the two enzymes, as shown by a strong positive correlation between total activities and active forms of phosphorylase and synthase. The enzyme activities responded as expected to stimuli such as insulin and glucose, which depressed phosphorylase and increased synthase activity, and glucagon, which increased phosphorylase and decreased synthase activity. In fasted animals approximately 50% of each enzyme was in the active form, which suggests the existence of a potential futile cycle for glycogen metabolism. The role for such a cycle in the regulation of glycogen synthesis and degradation is discussed.     

Studies on cartilage formation. XX. Histochemical investigation of some enzymes of glycogen metabolsim in regenerative articular surfaces.

In 28 dogs the distal articular cartilage of the femur was removed and the regenerating articular surface on the 70th postoperative day was studied histochemically for hexokinase, glucose-6-phosphatase, phosphohexose-isomerase, fructose-1, 6-diphosphatase, aldolase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, lactate dehydrogenase isoenzymes, phosphoglucomutase, phosphorylase, glycogen synthetase, UDP--glucose dehydrogenase, and UDP-glucuronic acid-4-epimerase. The articular surface consisted of fibrous tissue and of cartilage islets. The latter contained cells differentiating into cartilage and young chondrocytes. The glycolytic enzymes reacted positively in the regenerative articular surface. Enzyme activities were higher in the cells (particularly the chondroblasts and young chondrocytes) of the cartilage islets than in the connective tissue. In the cells differentiations into cartilage, beside the LDH isoenzymes characteristic of glycolysis, a significant LDH1 and LDH2 activity was observed. At the same site the presence of fructose-1, 6-diphosphatase-activity could be assumed, but there was no glucose-6-phosphatase activity. Glycogen synthesis proceeded in the cells of the cartilage islets and UDP-glucuronic acid-4-epimerase activity was observed in the differentiated cells. UDP-glucose dehydrogenase activity was positive in every section of the articular surface.     

Cerebral glucose and glycogen metabolism in diazinon-treated animals

The intraperitoneal (IP) treatment of rats with diazinon (40 mg/kg) resulted in a variety of changes in the brain. Glycogen was depleted, but there was an increase in the activities of glycogen phosphorylase, phosphoglucomutase, hexokinase, lactate dehydrogenase, and fructose 1,6 diphosphatase. The activity of glucose-6-phosphatase was unaffected while that of cholinesterase was significantly reduced. Lactic acid content was increased, while that of pyruvate was not altered. Animals developed tremors and convulsions, which were maximal two hours after treatment. The induced changes may be compensatory mechanisms to provide extra energy to cerebral tissue as a result of the stimulatory effects in diazinon-treated animals.     

Glyconeogenic and glycogenic enzymes in chronically active and normal skeletal muscle

The chronically active (pseudomyotonic) gastrocnemius muscle in the C57B16J dy2J/dy2J mouse contains both elevated lactate and glycogen as well as fibers that have high amounts of glycogen and enhanced glyconeogenic activity. In the present study we analyze the activities of some key glyconeogenic enzymes to assess the causes of elevated muscle glycogen and to determine the pathway for glycogen synthesis from lactate. Glycogen synthase, malate dehydrogenase, phosphoenolpyruvate carboxykinase, and malic enzyme were all elevated in homogenates of the chronically active muscle. Activities of glycogen phosphorylase and fructose 1,6-bisphosphatase were decreased in whole muscle homogenates. Histochemistry demonstrated that the high-glycogen fibers were typically fast-twitch glycolytic fibers that had high glycogen synthase, glycogen phosphorylase, and malic enzyme activities. Malate dehydrogenase activity followed succinate dehydrogenase activity and did not correlate to high-glycogen fibers. Thus the high-glycogen fibers have an elevated enzymatic capacity for glycogen synthesis from lactate, and the pathway may involve use of the pyruvate kinase bypass enzymes.     

Skeletal muscle glycogen content, structure, and metabolism are normal in rats with hepatic glycogen phosphorylase kinase deficiency

Skeletal muscle glycogen content and structure, and the activities of several enzymes of glycogen metabolism are reported for the hepatic glycogen phosphorylase b kinase deficient (gsd/gsd) rat. The skeletal muscle glycogen content of the fed gsd/gsd rat is 0.50 +/- 0.11% tissue wet weight, and after 40 hours of starvation this value is lowered 40% to 0.30 +/- 0.05% tissue wet weight. In contrast the gsd/gsd rat liver has an elevated glycogen content which remains high after starvation. The skeletal muscle phosphorylase b kinase, glycogen phosphorylase, glycogen synthase and acid alpha-glucosidase activities are 17.2 +/- 2.9 units/g tissue, 119.9 +/- 6.4 units/g tissue, 12.2 +/- 0.4 units/g tissue and 1.4 +/- 0.4 milliunits/g tissue, respectively, with approx. 20% of phosphorylase and approx. 24% of synthase in the active form (at rest). These enzyme activities resemble those of Wistar skeletal muscle, and again this contrasts with the situation in the liver where there are marked differences between the Wistar and the gsd/gsd rat. Fine structural analysis of the purified glycogen showed resemblance to other glycogens in branching pattern. Analysis of the molecular weight distribution of the purified glycogen indicated polydispersity with approx. 66% of the glycogen having a molecular weight of less than 250 X 10(6) daltons and approx. 25% greater than 500 X 10(6) daltons. This molecular weight distribution resembles those of purified Wistar liver and skeletal muscle glycogens and differs from that of the gsd/gsd liver glycogen which has an increased proportion of the low molecular weight material.(ABSTRACT TRUNCATED AT 250 WORDS)     

Biochemical changes in rat liver after 18.5 days of spaceflight

The effect of "weightlessness" on liver metabolism was examined using tissue from rats flown in earth orbit for 18.5 days aboard the Soviet Cosmos 936 biosatellite. Changes in the activities of certain carbohydrate and lipid enzymes were noted. Of the 28 hepatic enzyme activities assayed, two, palmitoyl-CoA desaturase and lactate dehydrogenase, increased, whereas five, glycogen phosphorylase, 6-phosphogluconate dehydrogenase, both acyltransferases which act on alpha-glycerolphosphate and diglycerides, and aconitate hydratase decreased. The remaining enzyme activities measured were unchanged. In addition, increased levels of liver glycogen and palmitoleate were noted which probably resulted from the lowered glycogen phosphorylase and increased palmitoyl-CoA desaturase activities, respectively, in those animals that experienced weightlessness. These changes caused by weightlessness were transient since all of the aforementioned alterations returned to normal values when measured in the livers of other rats which had flown in the biosatellite 25 days after recovery.     

Effects of altered thyroid status on beta-adrenergic actions on skeletal muscle glycogen metabolism

The effects of hypothyroidism on glycogen metabolism in rat skeletal muscle were studied using the perfused rat hindlimb preparation. Three weeks after propylthiouracil treatment, serum thyroxine was undetectable and muscle glycogen and Glc-6-P were decreased. Basal and epinephrine-stimulated phosphorylase a and phosphorylase b kinase activities were also significantly reduced, as were epinephrine-stimulated cAMP accumulation and cAMP-dependent protein kinase activity. Conversely, basal and epinephrine-stimulated glycogen synthase I activities were significantly higher while the Ka of the enzyme for Glc-6-P was lower in hypothyroid animals. Propylthiouracil-treated rats also had increased phosphoprotein phosphatase activities towards phosphorylase and glycogen synthase and decreased activity of phosphatase inhibitor 1. beta-Adrenergic receptor binding and basal and epinephrine-stimulated adenylate cyclase activities were reduced in muscle particulate fractions from hypothyroid rats. Administration of triiodothyronine to rats for 3 days after 3 weeks of propylthiouracil treatment restored the altered metabolic parameters to normal. It is proposed that the decreased beta-adrenergic responsiveness of the enzymes of glycogen metabolism in hypothyroid rat skeletal muscle is due to increased activity of phosphoprotein phosphatases and to reduced beta-adrenergic receptors and adenylate cyclase activity.     

Effect of denervation on the expression of glycogen phosphorylase in mouse skeletal muscle.

After sciatectomy of the left hind-limb of C57BL/J mice, a denervation-induced muscular atrophy ensued and was accompanied by a decrease in the specific activity of glycogen phosphorylase to approx. 25% of control values. The cofactor of phosphorylase, pyridoxal 5'-phosphate, was used as a specific label in the determination of the degradation rate of the enzyme following nerve section. After a delay of 3-4 days, phosphorylase was degraded approx, twice as rapidly in the denervated gastrocnemius (0.20 day-1) as in the control muscle (0.12 day-1). The effect of denervation on phosphorylase mRNA was measured by quantitative Northern-blot analysis using a rat skeletal-muscle phosphorylase cDNA probe. After an initial rapid decline, phosphorylase mRNA levels stabilized in denervated muscle at 50% of the value measured in the contralateral control muscle.     

Action of degradative enzymes on the light fraction of bovine septa protein polysaccharide

1. The administration of cortisol and of other glucocorticoid steroids to starved mice produced an increase in liver glycogen content, an elevation of glycogen-synthetase activity and a predominantly particulate localization of both phosphorylase and glycogen-synthetase enzymes. 2. Three daily doses of actinomycin D caused a marked glycogen depletion, a significant decrease in glycogen-synthetase activity, the solubilization of phosphorylase and glycogen synthetase and the following effects on the activities of various other enzymes: a decrease in UDP-glucose pyrophosphorylase and phosphoglucomutase, an increase in glucose 6-phosphate dehydrogenase and no change in glucose 6-phosphatase, 6-phosphogluconate dehydrogenase, pyruvate kinase and UDP-glucose dehydrogenase. 3. Glucose ingestion, but not cortisol administration, reversed the effects of actinomycin D on liver glycogen content and on the activities of phosphorylase and glycogen synthetase.     

Effect of hydrocortisone and glucagon on glycogen metabolism in the fetal rat liver.

1. Hydrocortisone increases in vivo incorporation of [14C] glucose into fetal liver glycogen in the last days of gestation, whereas in glucagon-treated fetuses, a slight decrease in the incorporation rate was found. 2. Hydrocortisone increases total synthetase activity as that of synthetase a but was without effect on fetal liver glycogen phosphorylase. 3. Glucagon causes a slight increase in phosphorylase a activity on days 19-21, and was without effect on the activities of synthetase a and total synthetase. 4. Dibutyryl cyclic AMP had no effect on the key enzymes of glycogen metabolism 1 h after injection in utero, whereas after 6 h an increase in phosphorylase a activity was found without any change in synthetase a activity.     

Hormonal control of endometrial glycogen metabolism in the Macaca arctoides

Endometrial biopsies obtained throughout the menstrual cycle of the Macaca arctoides show the glycogen content paralleling the serum progesterone fluctuations which occur during the menstrual cycle. Secretory phase samples contained a three-fold higher concentration of glycogen when compared to follicular phase tissue. Changes in the activity levels of the glycogen metabolizing enzymes, glycogen phosphorylase and glycogen synthetase, during various stages of the menstrual cycle are in accord with the concept that the post-ovulatory increase in endometrial metabolism is a function of progesterone influence on this tissue. Endometrial glycogen synthetase activity remains low during the early proliferative phase of the cycle and becomes significantly elevated (two-to three-fold) during the early secretory phase of the cycle. Glycogen phosphorylase shows a similar cyclicity later in the luteal phase, reaching maximal activity between the seventeenth to nineteenth day of the cycle and remaining elevated through the twenty-sixth day of the cycle. The coincident nature of the rise in peripheral progesterone to increases in uterine glycogen metabolism suggest that progesterone may be the prime modulator of uterine endometrial metabolism during the post-ovulatory phase.     

Role of the sympathoadrenal system in the regulation of glycogen metabolism in resting and exercising skeletal muscles.

The purpose of the present study was to characterize the role of catecholamines in the regulation of skeletal muscle glycogen metabolism during exercise. Using the rat hindlimb perfusion technique we have measured skeletal muscle glycogen content, glycogen phosphorylase and synthase activities in sympathectomized and/or demedullated rats under epinephrine treatment (10(-7) M) at rest and during muscle contraction. When epinephrine and/or norepinephrine deficiency was induced, muscle contraction resulted in a decrease in glycogen content (-63%) despite a decrease in glycogen phosphorylase activity ratio (0.25 to 0.11; p less than 0.001) and an increase in glycogen synthase activity ratio (0.13 to 0.27; p less than 0.001). Under these conditions, epinephrine treatment further reduced glycogen content while blunting the changes in the activity ratio of the rate-limiting enzymes. These data indicate that catecholamines do not play a primary role in skeletal muscle glycogen breakdown during acute exercise and suggest that allosteric regulators may be of prime importance.     

Age-related changes of glycogen metabolism in human fetal heart

The changes in the activities of three important glycogen metabolising enzymes, viz. glycogen synthetase, glycogen phosphorylase and alpha-D-glucosidase, along with glycogen content have been measured in adult human heart and human fetal heart collected at 13-36 weeks of gestation. At an early period, particularly 13-16 weeks of gestational age, the activity of glycogen synthetase and glycogen content were found to be maximum. However the activity of glycogen phosphorylase remained constant throughout the gestation and that of alpha-D-glucosidase showed a peak at 25-28 weeks of gestation, thereby indicating that fetal heart tissue has the capacity to utilise glycogen for energy.     

Characterization of 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) as an inhibitor of brain glycogen shunt activity

The pharmacological properties of 1,4-dideoxy-1,4-imino- d -arabinitol (DAB), a potent inhibitor of glycogen phosphorylase and synthase activity in liver preparations, were characterized in different brain tissue preparations as a prerequisite for using it as a tool to investigate brain glycogen metabolism. Its inhibitory effect on glycogen phosphorylase was studied in homogenates of brain tissue and astrocytes and IC₅₀-values close to 400 nM were found. However, the concentration of DAB needed for inhibition of glycogen shunt activity, i.e. glucose metabolism via glycogen, in intact astrocytes was almost three orders of magnitude higher. Additionally, such complete inhibition required a pre-incubation period, a finding possibly reflecting a limited permeability of the astrocytic membrane. DAB did not affect the accumulation of 2-deoxyglucose-6-phosphate indicating that the transport of DAB is not mediated by the glucose transporter. DAB had no effect on enzymes involving glucose-6-phosphate, i.e. glucose-6-phosphate dehydrogenase, phosphoglucoisomerase and hexokinase. Furthermore, DAB was evaluated in a functional preparation of the isolated mouse optic nerve, in which its presence severely reduced the ability to sustain evoked compound action potentials in the absence of glucose, a condition in which glycogen serves as an important energy substrate. Based on the experimental findings, DAB can be used to evaluate glycogen shunt activity and its functional importance in intact brain tissue and cells at a concentration of 300–1000 μM and a pre-incubation period of 1 h.     

Energy metabolism of the human fallopian tube.

The consumption of oxygen (QO2), the production of lactate and the profile of four key metabolic enzymes were measured in small samples of human oviductal mucosa (endosalpinx) removed at surgery. The QO2 in the absence of substrate was 3.4 microliters O2 (mg dry wt)-1 h-1, a value typical of quiescent tissue. The QO2 was stimulated by glucose, but diminished by glutamine and acetoacetate. Tissue lactate production was low and not increased by glucose. Hexokinase had the highest activity of the enzymes measured, followed by 2-oxoglutarate dehydrogenase; 6-phosphofructokinase and glycogen phosphorylase had low activities. The data are consistent with the proposition that glucose is a major metabolic fuel for human endosalpinx.     

Changes in the activity of enzymes,participating in glycogen metabolism of alloxan diabetic rats

Summary Alloxan diabetes induced in white rats by intraperitoneal injection of Aloxan-monohydrate (15 mg/100 g body weight) was used to study changes in the glycogen phosphorylase a and b, phosphoprotein phosphatases and hexokinase activities under insulin deficiency conditions. Among the enzymes studied, an increase in muscle phosphorylase a activity as well as the a/b ratio have been obtained. In diabetic muscle phosphoprotein phosphatases and hexokinase activities were diminished.AMP increased the liver glycogen phosphorylase activity twice in diabetic rats whereas in normal animals the enzyme was less sensitive to this effector. The changes in liver hexokinase activity at diabetes were not connected and correlated with the altered phosphorylase and protein phosphatase activities.The logical chain of probable molecular events taking place in muscle glycogen metabolism under the conditions of insulin deficiency is offered.     

Changes in the acinar distribution of some enzymes involved in carbohydrate metabolism in rat liver parenchyma after experimentally induced cholestasis

Extrahepatic cholestasis induced by ligation and transsection of the common bile duct caused a change in the parenchyma/stroma relationship in rat liver. Two weeks after ligation, the periportal zones of the parenchyma were progressively invaded by expanding bile ductules with surrounding connective tissue diverging from the portal areas. Parenchymal disarray developed and small clumps of hepatocytes or isolated hepatocytes were scattered within the expanded portal areas. These cells showed normal activity of lactate, succinate and glutamate dehydrogenase and may, therefore, be considered to be functionally active. After cholestasis the remainder of the liver parenchyma showed adaptational changes with respect to glucose homeostasis, as demonstrated by histochemical means. Glycogen stores disappeared completely whereas glycogen phosphorylase activity increased about ten fold. The increased glycogen phosphorylase activity and glycogen depletion indicate a greater glycogenolytic capacity in liver parenchyma after bile duct ligation to maintain as far as possible a normal plasma glucose concentration. The parenchymal distribution pattern of glucose-6-phosphatase activity did not change significantly after bile duct ligation. The isolated hepatocytes within the expanded portal tracts showed a high activity of this enzyme whereas the pericentral parenchyma was only moderately active. The distribution patterns of glucose-6-phosphate dehydrogenase and lactate dehydrogenase activity in the liver parenchyma were also largely unchanged after bile duct ligation, but the histochemical reaction for glucose-6-phosphate dehydrogenase activity demonstrated infiltration of the remainder of the parenchyma by non-parenchymal cells, possibly Küpffer cells and leucocytes as part of an inflammatory reaction. Under normal conditions the mitochondrial enzymes succinate and glutamate dehydrogenase show an opposite heterogenous distribution pattern in liver parenchyma. Following cholestasis both enzymes became uniformly distributed. The underlying regulatory mechanism for these different changes in distribution patterns of enzyme activities is not yet understood.     

Effects of denervation on the activities of some tricarboxylic acid-cycle-associated dehydrogenases and adenine-metabolizing enzymes in rat diaphragm muscle

1. The activity of several tricarboxylic acid-cycle-associated dehydrogenases, adenine-metabolizing enzymes and glutathione reductase and the content of myoglobin were measured in rat diaphragm muscle after unilateral nerve section. 2. Consistent with morphological disintegration of the mitochondria there was a rapid diminution in activity of NAD- and NADP-linked isocitrate dehydrogenase, malate dehydrogenase and glutamate dehydrogenase. 3. Creatine phosphokinase and adenylate kinase, by contrast, showed little change in activity; adenylate deaminase and glutathione reductase activities increased during the hypertrophic phase. The concentration of myoglobin at first declined, then increased again. 4. The distribution of enzymes between the left and right hemidiaphragms was found not to be uniform. 5. Activities of adenine-metabolizing enzymes in the diaphragm were as great as in white muscle. It is suggested that their reputedly lower activities in red muscle properly refer to muscle containing a high proportion of intermediate fibres, which is not the case with diaphragm. 6. The possible causes of the transient hypertrophy after nerve section are discussed.