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Results for “glucose metabolism”

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At least 19 recordsLinked to original sources

PubMed1979

Effects of electric stress on glucose metabolism, glucose-stimulated cyclic adenosine 3',5'-monophosphate accumulation and 45 Ca++ efflux in isolated pancreatic islets from rats fed with a high fat diet.

The effects of the electric stress on glucose oxidation, cyclic adenosine 3', 5'-monophosphate (AMP) accumulation and 45Ca++ efflux in response to glucose were studied in pancreatic islets isolated from rats fed on a control (C) or a high fat diet (F) for 12 weeks. The half of rats on each diet were subjected to electrical shocks in the random time schedule for 1 hr per day for the last 3 weeks of the feeding period (group C-S and F-S). The remaining rats were not given any shocks (group C-NS and F-NS). The rats in F-S group had the high levels of plasma epinephrine, dopamine and blood glucose. The basal content of cyclic AMP after 20 min of incubation with 2.8 mM glucose was decreased in islets from F-S group without affecting insulin release. After 20 min of incubation with 25 mM glucose, the cyclic AMP content in islets from F-S group, which was identical with that in F-NS group, was only 50% of that in C-S group. Insulin release in response to high glucose was significantly inhibited in islets from F-S group. In spite of a remarkable increase of cyclic AMP content in islets from C-S group, insulin release did not differ from that in C-NS group. Glucose (16.7 mM)-stimulated 45Ca++ efflux from the perfused islets was greatly inhibited by the high fat diet rather than by stress. The rate of glucose oxidation with 16.7 mM glucose was decreased in islets from F-S group. It is suggested that the decreased insulin release in response to glucose provoked by the combined effects of the feeding of a high fat diet and electric stress may be mediated by changes of the adenylate cyclase-cyclic AMP system on the plasma membrane of the B-cell or be related to changes in glucose metabolism in islets.

Adrenal Cortex↗

PubMed1975

Hormonal control of glucose metabolism.

Glucose homeostasis is accomplished through two major hormones, glucagon and insulin. These hormones, of course, must work in concert with other permissive hormones such as glucocorticoids and catecholamines to bring about a multiplicity of physiological processes such as gluconeogenesis, glycolysis, lipolysis, and proteolysis that maintain the organism's biochemical integrity.

Blood Glucose↗

PubMed1979

Effects of insulin on glucose metabolism and glucose transport in fat cells of hormone-treated hypophysectomized rats: evidence that growth hormone restricts glucose transport.

In earlier studies we have shown that insulin does not stimulate glucose incorporation in adipocytes of hypophysectomized (hypox) rats. Basal glucose incorporation is decreased, although basal 3-O-methylglycose transport is very rapid and cannot be further stimulated by insulin. In this study we treated hypox rats with human GH, ACTH, and T3, alone or in combination, and examined the effects of insulin on glucose incorporation into fat cells and on 3-O-methylglucose transport. The results show that chronic administration of T3 alone to hypox rats partially restores glucose incorporation into fat cells and, in combination with ACTH, completely restores this incorporation. The two hormones have no effect on the glucose carrier system. The transport rate under T3 and ACTH replacement therapy continues to proceed at a maximal rate, so that basal glucose incorporation is high but not further enhanced by insulin. In contrast, administration of human GH to hypox rats does not influence glucose incorporation but has a marked effect on glucose transport. The basal glucose transport rate returns toward normal and again responds to insulin. This suggests 1) that enzyme activities responsible for the lipogenetic capacity of the fat cell are decreased in hypox rats and returned toward normal by the combined T3/ACTH treatment, and 2) that the limitation of glucose transport in the fat cell is controlled by GH. GH seems to induce a change of the glucose-carrier system; it leads to a restriction of glucose transport, which is acutely modulated by insulin.

Adipose Tissue↗

PubMed1978

Glucose metabolism in Pycnoporus cinnabarinus.

It was demonstrated by the measurement of enzyme activities and by radiorespirometric assays that the basidiomycete Pycnoporus cinnabarinus metabolizes glucose through the glycolytic pathway and the pentose phosphate cycle.

Basidiomycota↗

PubMed1978

Effect of pH on the growth and glucose metabolism of Neisseria gonorrhoeae.

This study examined the effect of pH on the metabolism of glucose by Neisseria gonorrhoeae. Radiorespirometric studies revealed that cells growing at pH 7.2 or 8.0 metabolized glucose primarily (ca. 80%) via the Entner-Doudoroff pathway. The remainder of the glucose was metabolized via the pentose phosphate pathway (ca. 20%). The tricarboxylic acid cycle was not active during glucose catabolism at either pH 7.2 or 8.0, and acetate accumulated in the medium. Cells growing at pH 6.0 had markedly increased pentose phosphate pathway activity (ca. 50%) and a functioning tricarboxylic acid cycle. The alteration in pathways was not due to differences in growth rate, but to the pH of the medium. Chemical fractionation of labeled cells and total hexose analyses revealed that growth pH markedly affected the composition of the gonococcus.

Acetates↗

PubMed1979

Effect of experimental hyperinsulinaemia on intracellular glucose metabolism of isolated adipocytes.

Glucose oxidation and lipogenesis were studied in isolated adipocytes from control and non-obese, experimentally hyperinsulinaemic rats. In cells from the hyperinsulinaemic animals oxidation of either [1(-14) C]- or [6(-14) C] glucose was increased in the presence or absence of insulin, at substrate concentrations from 0.1 to 20 mmol/l. Glucose incorporation into total triglycerides and fatty acids was also increased. These enhanced rates of glucose metabolism were due to increased activity of the glucose transport system in addition to increased activity of intracellular glucose metabolism. Therefore, these data indicate that insulin can influence long term glucose homoeostasis by augmenting the overall cellular capacity for glucose metabolism at several loci.

Adipose Tissue↗

PubMed1976

Influence of growth temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus.

The influence of temperature on glucose metabolism of a psychotrophic strain of Bacillus cereus was investigated. The pH of the growth medium and spore-forming frequencies of B. cereus varied when grown at 32, 20, or 7 C. Radiorespirometric analyses revealed that vegetative cells of B. cereus metabolized glucose by simultaneous operation of the Embden-Meyerhof-Parnas pathway and the pentose phosphate pathway. As the growth temperature decreased, glucose was metabolized with increased participation of the pentose phosphate pathway. The shift of cells grown at a higher temperature to a lower temperature increased the relative participation of the pentose phosphate pathway, whereas the shift of cells grown at low temperatures to a higher temperature had the opposite effect. Cells of late logarithmic phase grown at 20 and 7 C oxidized acetate by the tricarboxylic acid cycle reaction. However, cells grown at 32 C failed to oxidize acetate to CO2 to any appreciable extent. The extracellular products resulting from the metabolism of glucose decreased as the growth temperature was lowered. Organic acids were the major extracellular products of cultures grown at 32 and 20 C. Acetic acid, lactic acid, and pyruvic acid together accounted for 86.1 and 78.9% of extracellular radioactivity, respectively, at the two temperatures. The relative ratio of these three acids varied between the temperatures. Little or no acid accumulated at 7 C.

Acetates↗

PubMed1978

Relationship between the rate of H+ transport and pathways of glucose metabolism by turtle urinary bladder.

The urinary bladder of the fresh-water turtle acidifies its contents by actively transporting H(+) ions across the luminal membrane. It is known that the H(+) transport system is dependent upon oxidative metabolism and the substrate glucose; however, the specific biochemical events resulting in H(+) translocation have not been identified. This study examines the relationship between active H(+) transport and a specific oxidative pathway of glucose metabolism, the pentose phosphate shunt. To investigate this relationship the metabolic and transport rates were simultaneously measured under several well-defined conditions. When H(+) transport was inhibited by either the application of an opposing pH gradient or by acetazolamide, glucose metabolism by the pentose phosphate shunt declined. Conversely, stimulation of H(+) transport by either imposing a more favorable pH gradient or by CO(2) addition resulted in an increase in pentose phosphate shunt metabolism. Glycolytic activity, in contrast, was invariant with the maneuvers which altered the rate of H(+) transport. Additional experiments localized pentose phosphate shunt enzyme activity to the mucosal fraction of the bladder which is the cell layer responsible for acid secretion. The finding that the rate of glucose metabolism by the pentose phosphate shunt is related to the rate of H(+) transport suggests but does not prove that the pentose phosphate shunt may be an important metabolic pathway for H(+) transport by the turtle urinary bladder.

Acetazolamide↗

PubMed1976

Inhibition of glucose metabolism by n-hexadecane in Cladosporium (Amorphotheca) resinae.

When Cladosporium resinae is provided with n-hexadecane and glucose, n-hexadecane is used preferentially. Studies using [14C]glucose indicated that n-hexadecane did not inhibit glucose uptake but did retard oxidation of glucose to CO2 and assimilation of glucose carbon into trichloroacetic acid-insoluble material. Glucose could be recovered quantitatively from hydrocarbon-grown cells that had been transferred to glucose. Four enzymes that may be involved in glucose metabolism, hexokinase, glucose-6-phosphate dehydrogenase, glucose-phosphate isomerase, and succinate dehydrogenase, were not detected in cells grown on hexadecane but were present in cells grown on glucose. Addition of hexadecane to extracts of glucose-grown cells resulted in immediate loss of activity for each of the four enzymes, but two other enzymes did not directly involved in glucose metabolism, adenosine triphosphatase and alanine-ketoacid aminotransferase, were not inhibited by hexadecane in vitro. Cells grown on hexadecane and transferred to glucose metabolize intracellular hexadecane; after 1 day, activity of hexokinase, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, and succinate dehydrogenase could be detected and 22% of the intracellular hydrocarbon had been metabolized. Hexadecane-grown cells transferred to glucose plus cycloheximide showed the same level of activity of all the four enzymes as cells transferred to glucose alone. Thus, intracellular n-hexadecane or a metabolite of hexadecane can inthesis of those enzymes is not inhibited.

Adenosine Triphosphatases↗

PubMed1978

Glucose metabolism by adult hepatocytes in primary culture and by cell lines from rat liver.

The metabolic fate of [U-14C]glucose has been examined in detail in adult rat hepatocytes in primary monolayer culture, as well as in two permanent cell lines--Buffalo rat liver (BRL) and transplantable rat hepatoma (HTC) cells-derived from normal rat liver and from rat hepatoma, respectively. Under defined conditions of incubation, at a glucose concentration of 5.5 mM, the three types of cultured liver cells exhibited pronounced differences in glucose metabolism. Primary cultures, like the intact liver, differed from the cell lines in consuming relatively small amounts of glucose and converting approximately 50% of the total metabolized glucose to lactate. By contrast, the permantent cell lines consumed glucose at a 40-fold greater rate than did primary cultures, converting 80--90% of the carbohydrate to lactate. Oxidative metabolism of glucose carbon also differed among the three types of liver culture. Of the total [U-14C]glucose consumed, primary cultures converted approximately 30% to labeled CO2 per hour, whereas the liver cell lines converted 5--10%. Finally, glucose metabolism in primary culture exhibited adaptation as hepatocytes aged in culture, shifting progressively toward the pattern exhibited by the permanent cell lines. This change occurred over a time course similar to that for other kinds of functional change in hepatocytes in primary culture and thus may be relevant to the general problem of phenotypic alteration in liver cell culture.

Adenosine Triphosphate↗

PubMed1977

Effects of insulin and NSILA on adipocytes of normal and diabetic rats: receptor binding, glucose transport and glucose metabolism.

Isolated fat cells from normal and streptozotocin-diabetic rats were compared with respect to metabolic indices (glucose-uptake, 3-0-methyl-glucose efflux) with and without stimulation by insulin and nonsuppressible insulin-like activity (NSI-LA). In addition, binding studies were carried out with these two hormones. Basal 14C-glucose oxidation and incorporation into lipids was decreased in diabetic cells and their response to insulin and NSILA was greatly reduced. Basal efflux of 3-0-methylglucose from diabetic cells was somewhat faster than from normal cells. The response to insulin and NSILA was less than in normal cells and it was delayed. The apparent number of insulin binding sites as well as their affinity for insulin was increased in diabetic cells. In contrast, the apparent number of binding sites for NSILA was decreased in diabetic cells and their affinity for NSILA was increased. In normal cells insulin enhanced binding of 125I-NSILA more markedly than in diabetic cells. These findings show that the rate-limiting step of impaired glucose metabolism (oxidation and lipogenesis) in diabetic fat cells is beyond the interaction of the hormone with the receptor. They suggest that the apparent number of hormone receptors (insulin, NSILA) on the cell membrane is regulated individually for each binding site.

Adipose Tissue↗

PubMed1979

Biphasic alterations in glucose metabolism by soleus muscle from the burned limb.

Tissue temperature and in vitro glucose metabolism by rat soleus muscle were studied following a 3-second burn on one hind limb in 90 degrees C water. The injury increased the subcutaneous temperature in the calf of the burned limb to 53.4 +/- 0.7 (SE) degrees C and that between soleus muscle and fibula to 49.4 +/- 1.3 degrees C, both temperatures returning to normal at approximately 3 minutes postburn. The injury resulted in biphasic alterations in glucose metabolism by the soleus muscle from the burned limb; glucose uptake and lactate release were depressed at 4 hours but were elevated above control levels at 3 days postburn. The maintenance of an approximate 1:2 ratio of glucose uptake to lactate release suggested that changes in glucose uptake reflected primarily conversion to tricarbon units rather than changes in the rate of glucose oxidation. Since glucose metabolism by soleus muscle from contralateral unburned limb of injured animals did not differ from controls at any of the test times, the changes in the burned limb were not likely the result of systemic alterations in metabolic and endocrine environment. The biphasic alterations did not correlate with the degree of soleus muscle edema. It is concluded that proximity to the burn wound is a new determinant of abnormal glucose utilization by skeletal muscle.

Animals↗

PubMed1976

Glucose metabolism in isolated fat cells: enhanced response of larger adipocytes from older rats to epinephrine and adrenocorticotropin.

The effects of insulin and of two lipolytic hormones (epinephrine and ACTH1) on the rate and pattern of glucose metabolism were compared during incubation of isolated fat cells, obtained from epididymal fat pads of rats of varying age and degrees of adiposity. Glucose metabolism and the intracellular free fatty acid levels were expressed on a per cell basis and in relation to adipocyte size. The data for total glucose metabolism show that, in contrast to the declining insulin effect observed with adipocyte enlargement, the stimulation of glucose uptake and metabolism by these lipolytic hormones was significantly greater in the larger fat cells from the older fatter rats than in the smaller ones from the younger leaner rats. Lipolytic hormones suppressed, whereas insulin enhanced, fatty acid synthesis; moreover the lipolytic hormones stiumlated glucose ce effect of epinephrine on the intracellular free fatty acid levels was greater in the small fat cells than in the large ones; this effect of epinephrine was markedly curtained by the presence of glucose in the incubation medium, making it unlikely that acceleration of glucose metabolism by the lipolytic stimulus was mediated by an elevation of the intracellular free fatty acid level. The present results show a markedly enhanced capacity of the large adipocytes to accelerate glucose metabolism in response to these liplytic hormones. Thus, in contrast to prevailing notions of declining hormonal responsiveness with expanding fat cell size in older and more obese animals, this study documents an instance of increased hormonal response in enlarged adipocytes and points to the need for a more comprehensive reevaluation of the various hormonal effects in adipocytes of different size.

Adipose Tissue↗

PubMed1979

Local cerebral glucose metabolism during controlled hypoxemia in rats.

2-Deoxy-[14C]glucose metabolism was examined in brains of hypoxic, normotensive rats by autoradiography, which revealed alternating cortical columns of high and low metabolism. Activity in white matter was increased severalfold over that in adjacent gray matter. The columns were anatomically related to penetrating cortical arteries with areas between arteries demonstrating higher rates of metabolism. The results suggest the presence of interarterial tissue oxygen gradients that influence regional glucose metabolism. The relatively greater sensitivity of white matter metabolism to hypoxia may lead to an understanding of white matter damage in postanoxic leukoencephalopathy.

Animals↗

PubMed1976

The role of glucose limitation in the regulation of the transport of glucose, gluconate and 2-oxogluconate, and of glucose metabolism in Pseudomonas aeruginosa.

The pathway of glucose metabolism in Pseudomonas aeruginosa was regulated by the availability of glucose and related compounds. On changing from an ammonium limitation to a glucose limitation, the organism responded by adjusting its metabolism substantially from the extracellular direct oxidative pathway to the intracellular phosphorylative route. This change was achieved by repression of the transport systems for gluconate and 2-oxogluconate and of the associated enzymes for 2-oxogluconate metabolism and gluconate kinase, while increasing the levels of glucose transport, hexokinase and glucose 6-phosphate dehydrogenase. The role of gluconate, produced by the action of glucose dehydrogenase, as a major inhibitory factor for glucose transport, and the possible significance of these regulatory mechanisms to the organism in its natural environment, are discussed.

Alcohol Oxidoreductases↗

PubMed1979

Effect of administration of 5-hydroxytryptophan and an inhibitor of L-aromatic amino acid decarboxylase on glucose metabolism in rat brain.

The effect of 5-hydroxytryptophan (5-HTP)--the precursor of serotonin (5-hydroxytryptamine, 5-HT)--and of an inhibitor, N-(DL-seryl)-N'-(2,3,4-trihydroxybenzyl)hydrazine (Ro4-4602), of L-aromatic amino acid decarboxylase on the metabolism of glucose to amino acids in brain tissue was investigated. Labeled glucose (20 muCi, 0.24 mg in 0.2 ml 0.9% saline) was injected intravenously into fed rats pretreated with Ro4-4602 (50 mg/kg intraperitoneally) either alone or in combination with 5-HTP (30 mg/kg intravenously) or with the appropriate vehicle. After the injection of Ro4-4602 plus 5-HTP, the concentrations of 5-HT and 5-HTP in brain were increased, but the increase of 5-HTP was more pronounced and prolonged than the increase in 5-HT. This suggested that Ro4-4602 slightly inhibits the reaction of decarboxylation in the brain, although at the dose used the drug is usually considered to act only peripherally. After administration of Ro4-4602 alone or combined with 5-HTP, the concentration of glucose in plasma was not significantly increased. However, the concentration of glucose in brain was markedly increased with such treatments. The administration of Ro4-4602 alone or combined with 5-HTP reduced the flux of 14C from labeled glucose to amino acids in brain. The concentrations of amino acids in brain were little changed by these treatments.

5-Hydroxytryptophan↗

PubMed1977

Enzymes of glucose metabolism in palmar fascia and Dupuytren's contracture.

Several enzymes participating in glucose metabolism and some of the acid hydrolases were assayed in palmar fascia and Dupuytren's contracture with fluorometric microanalytical methods. The enzyme activities of glucose metabolism were lower in normal palmar fascia than in dermis. The fascia of Dupuytren's contracture exhibited a general increase in the enzyme activities of glucose catabolism. Little alteration was found in alanine aminotransferase and UDP-glucose dehydrogenase activity in the lesion. Lysosomal hydrolytic enzyme activities were increased five to ten times in Dupuytren's tissue. The dermis overlying Dupuytren's contracture exhibited an increase in the enzyme activities of glucose catabolism, but to a lesser degree than did the fascia of the lesion. The epidermis of involved palmar skin displayed normal enzyme activities.

Acid Phosphatase↗

PubMed1978

Bioenergetic aspects of aerobic glucose metabolism of Escherichia coli K-12 under varying specific growth rates and glucose concentrations.

An attempt was made to find a bioenergetical explanation for the differential effect of specific growth rate and glucose concentration on glucose metabolism of Escherichia coli K-12 with the help of 2,4-dinitrophenol (DNP). The effect of DNP on biomass occurred only at high glucose concentrations. The presence of this uncoupler strongly stimulated glucose uptake rates and oxygen uptake rates, but repressed severly Yg values. Increase in glucose concentration, however, sharply decreased QO2. The amount of oxygen required for maintenance was not affected by DNP, but Yomax values were much lower in the presence of DNP. The results are discussed and it is suggested that aerobic fermentation is caused by a severe reduction of site 1 of the respiratory chain region, whereas biomass formation is affected by repression of the terminal cytochrome a2. In comparing the effect of glucose on biomass formation at similar Qglucose levels aerobic and anaerobic fermentation, repression occurred in both cases at glucose concentrations of 0.3% and above. Although the analyses of 15 enzymes established the metabolic differences, the repression of growth was common to both fermentation types.

Aerobiosis↗