scholarly journals Stimulation by iodide of H2O2generation in thyroid slices from several species

2000 ◽  
Vol 278 (4) ◽  
pp. E692-E699 ◽  
Author(s):  
B. Corvilain ◽  
L. Collyn ◽  
J. van Sande ◽  
J. E. Dumont
Keyword(s):  
Thyroid Hormones ◽  
Pentose Phosphate Pathway ◽  
Glucose Oxidation ◽  
Inhibitory Effect ◽  
Pentose Phosphate ◽  
Human Thyroid ◽  
Acute Administration ◽  
Dual Control ◽  
Inhibitory Effects ◽  
Thyroid Metabolism

The regulation of thyroid metabolism by iodide involves numerous inhibitory effects. However, in unstimulated dog thyroid slices, a small inconstant stimulatory effect of iodide on H2O2 generation is observed. The only other stimulatory effect reported with iodide is on [1-14C]glucose oxidation, i.e., on the pentose phosphate pathway. Because we have recently demonstrated that the pentose phosphate pathway is controlled by H2O2generation, we study here the effect of iodide on basal H2O2 generation in thyroid slices from several species. Our data show that in sheep, pig, bovine, and to a lesser extent dog thyroid, iodide had a stimulatory effect on H2O2 generation. In horse and human thyroid, an inconstant effect was observed. We demonstrate in dogs that the stimulatory effect of iodide is greater in thyroids deprived of iodide, raising the possibility that differences in thyroid iodide pool may account, at least in part, for the differences between the different species studied. This represents the first demonstration of an activation by iodide of a specialized thyroid function. In comparison with conditions in which an inhibitory effect of iodide on H2O2 generation is observed, the stimulating effect was observed for lower concentrations and for a shorter incubation time with iodide. Such a dual control of H2O2 generation by iodide has the physiological interest of promoting an efficient oxidation of iodide when the substrate is provided to a deficient gland and of avoiding excessive oxidation of iodide and thus synthesis of thyroid hormones when it is in excess. The activation of H2O2 generation may also explain the well described toxic effect of acute administration of iodide on iodine-depleted thyroids.

Glucose oxidation in white adipose tissue from BIO 14.6 dystrophic hamsters

1986 ◽  
Vol 64 (10) ◽  
pp. 1321-1324
Author(s):  
J. Elbrink ◽  
E. G. Hunter
Keyword(s):  
Skeletal Muscle ◽  
Adipose Tissue ◽  
White Adipose Tissue ◽  
Pentose Phosphate Pathway ◽  
Glucose Oxidation ◽  
Pentose Phosphate ◽  
Muscle Degeneration ◽  
Functional Integrity ◽  
Enhanced Activity ◽  
Retroperitoneal Adipose Tissue

In studies of glucose oxidation in white retroperitoneal adipose tissue of BIO 14.6 dystrophic and FIB normal hamsters aged 55–67 and 368–379 days, no difference was found in the basal state of radiolabelled 14CO2 production using either D-[6-14C]glucose or D-[1-14C]glucose. When C6-labelled glucose was used, insulin induced a slightly greater increase in glucose oxidation in dystrophic adipose tissue at both ages. When C1-labelled glucose was used, insulin enhanced glucose oxidation in dystrophic tissue more than twice normal in tissues from young animals and five times normal in tissues from the old ones. The increase in oxidation with D-[1-14C]glucose likely represents enhanced activity of the pentose phosphate pathway, which has also been observed in certain tissues of other animals with inherited skeletal-muscle degeneration. The change can probably be classified as being compensatory, an attempt by tissues to maintain functional integrity.

A comparison of the effects of acute verses chronic administration of phenoxybenzamine on pressor responses elicited by the selective α1-adrenoceptor agonist cirazoline in the pithed rat preparation

1992 ◽  
Vol 70 (6) ◽  
pp. 916-921 ◽  
Author(s):  
Reza Tabrizchi ◽  
Christopher R. Triggle
Keyword(s):  
Pressor Response ◽  
Chronic Administration ◽  
Inhibitory Effect ◽  
Acute Administration ◽  
Dependent Manner ◽  
Pithed Rat ◽  
Inhibitory Effects ◽  
Receptor Reserve ◽  
Pressor Responses ◽  
The Right

The effects of nifedipine on the pressor responses to cirazoline were examined in the pithed rat preparation that had received either acute or chronic phenoxybenzamine treatment. Phenoxybenzamine was administered, i.v., to conscious rats, either acutely at 0.01, 0.03, and 0.1 mg/kg, 60 min prior to the commencement of the experiments or chronically at 0.1, 0.3, and 1.0 mg/kg, once daily for 7 days. Nifedipine was administered i.a. (1.0 mg/kg) after the animals had been pithed. The acute or chronic administration of phenoxybenzamine alone displaced the dose–response curve to cirazoline to the right in a dose-dependent manner, while reducing the slope function and maximum response to the agonist. The combined effects of acute phenoxybenzamine and nifedipine produced an additive inhibitory effect on the pressor response elicited by cirazoline, which was most apparent following the removal of receptor reserve by acute phenoxybenzamine. The inhibitory effects of nifedipine and chronically administered phenoxybenzamine were additive at the lower administered doses of the alkylating agent but, in contrast with the effects of acute phenoxybenzamine, the enhanced inhibitory effects of nifedipine were reduced following the removal of receptor reserve. These results indicate that the chronic administration of phenoxybenzamine reduces the additive inhibitory effects of nifedipine and phenoxybenzamine that were observed following the acute administration of phenoxybenzamine.Key words: α1-adrenoceptors, vasoconstriction, subtypes, pithed rat, calcium channel antagonist.

Metabolic activities of sheep erythrocytes. I. Glycolytic activities

1962 ◽  
Vol 13 (1) ◽  
pp. 31 ◽  
Author(s):  
RA Leng ◽  
EF Annison
Keyword(s):  
Carbon Dioxide ◽  
Methylene Blue ◽  
Lactic Acid ◽  
Oxygen Uptake ◽  
Pentose Phosphate Pathway ◽  
Glucose Oxidation ◽  
Lactic Acid Production ◽  
Pentose Phosphate ◽  
Sheep Erythrocytes ◽  
Metabolic Activities

Sheep erythrocytes, which in most animals are impermeable to glucose, show low glycolytic activities relative to human cells. When 14C-labelled glucose was incubated with erythrocyte suspensions the oxygen uptake was 10.9 ± 1.8 µl/hr/ml of cells (5 replications), and glucose oxidation (measured by recovery of [14C]carbon dioxide) was 0.03 ± 0.007 µmole/hr/ml (5). Addition of methylene blue (0.4 µmole/ ml) increased oxygen uptake to 56 ± 3.5 µl/hr/ml (5) and glucose oxidation to 0.36 ± 0.02 µmole/hr/ml. Lactic acid production was increased from 1 .5 ± 0.06 µmole/hr/ml (7) to 1.7 ± 0.11 µmole/hr/ml (7) in the presence of methylene blue. Comparison of the yields of [14C]carbon dioxide from [1-14C]glucose and uniformly labelled [14C]glucose indicated that when stimulated by methylene blue 80–100% of glycolysis proceeded by the pentose phosphate pathway, but in the unstimulated system the alternative aerobic pathway accounted for only about 15% of total glycolysis.

Effects of insulin, glucocorticoids and thyroid hormones on the activities of key enzymes of glycolysis, glutaminolysis, the pentose-phosphate pathway and the Krebs cycle in rat macrophages

1992 ◽  
Vol 135 (2) ◽  
pp. 213-219 ◽  
Author(s):  
L. F. B. P. Costa Rosa ◽  
Y. Cury ◽  
R. Curi
Keyword(s):  
Thyroid Hormones ◽  
Pentose Phosphate Pathway ◽  
Culture Medium ◽  
Citrate Synthase ◽  
Inflammatory Responses ◽  
Krebs Cycle ◽  
Pentose Phosphate ◽  
Macrophage Phagocytosis ◽  
And Function ◽  
Glucose 6 Phosphate Dehydrogenase

ABSTRACT In the present study the effects of insulin, glucocorticoids and thyroid hormones on macrophage metabolism and function were investigated. The maximum activities of hexokinase, glucose-6-phosphate dehydrogenase, glutaminase and citrate synthase were determined in macrophages obtained from hormonetreated rats and those cultured for a period of 48 h in the presence of hormones. Macrophage phagocytosis was markedly inhibited by dexamethasone and thyroid hormones, remaining unchanged when insulin was added to the culture medium, however. The changes in the enzyme activities caused by hormone treatments of the rats were very similar to those found in culture. Insulin enhanced citrate synthase and hexokinase activities and diminished those of glutaminase and glucose-6-phosphate dehydrogenase. Dexamethasone had a similar effect except on glucose6-phosphate dehydrogenase. The addition of thyroid hormones to the culture medium raised the activities of glutaminase and hexokinase and reduced that of citrate synthase. The results presented support the suggestion that the effects of insulin, glucocorticoids and thyroid hormones on immune and inflammatory responses could well be mediated through changes in macrophage metabolism.. Journal of Endocrinology (1992) 135, 213–219

Effect of acetazoleamide on thyroid metabolism

1959 ◽  
Vol 196 (2) ◽  
pp. 291-294 ◽  
Author(s):  
D. T. Krieger ◽  
A. Moses ◽  
H. Ziffer ◽  
J. L. Gabrilove ◽  
L. J. Soffer
Keyword(s):  
Carbonic Anhydrase ◽  
Radioactive Iodine ◽  
Thyroid Tissue ◽  
Inhibitory Effect ◽  
Iodine Uptake ◽  
Human Thyroid ◽  
Inhibitory Potency ◽  
Thyroid Metabolism ◽  
Radioactive Iodine Uptake

Previous studies showed Diamox (acetazoleamide) to be an effective depressant of thyroidal radioactive iodine uptake. It was hypothesized that this effect was mediated via carbonic anhydrase inhibition. The presence of carbonic anhydrase was demonstrated in rat and human thyroid tissue. Diamox and other sulfonamide like drugs were tested for their relative carbonic anhydrase inhibitory potency and depressant effect on in vitro radioactive iodine uptake. No correlation between these two effects could be observed, and carbonic anhydrase addition did not reverse the inhibitory effect of Diamox. These experiments therefore fail to provide an explanation of the mechanism of depression of thyroidal radioactive iodine uptake by Diamox.

Pathways of carbohydrate metabolism in Mycobacterium tuberculosis H37Rv

1975 ◽  
Vol 21 (11) ◽  
pp. 1688-1691 ◽  
Author(s):  
N. Jayanthi Bai ◽  
M. Ramachandra Pai ◽  
P. Suryanarayana Murthy ◽  
T. A. Venkitasubramanian
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Carbohydrate Metabolism ◽  
Pentose Phosphate Pathway ◽  
Glucose Oxidation ◽  
Pentose Phosphate ◽  
Tuberculosis H37rv ◽  
Mycobacterium Tuberculosis H37rv ◽  
Cellular Components

Radiorespirometric studies using glucose labelled at 1, 2, 3–4, and 6 positions and enzymatic studies were conducted to determine the primary pathways of glucose dissimilation in Mycobacterium tuberculosis H37Rv. The pattern of 14CO2 recovery was C3−4 > C1 > C6 = C2. The Embden–Meyerhof pathway was found to be the predominant pathway for glucose oxidation, operative to the extent of 94%. The pentose phosphate pathway accounted for the remaining 6%. Maximum incorporation of 14C into cellular components was from C2 and C6 labelled glucose.

scholarly journals Comparative feature of the glucose metabolism in liver of the rats under acute alcohol and morphine intoxication

2011 ◽  
Vol 57 (6) ◽  
pp. 615-623
Author(s):  
S.V. Lelevich
Keyword(s):  
Comparative Analysis ◽  
Glucose Metabolism ◽  
Pentose Phosphate Pathway ◽  
Inhibitory Effect ◽  
Pentose Phosphate ◽  
Comparative Feature ◽  
Dose Dependent

The comparative analysis effect of acute alcohol and morphine intoxications on rats on hepatic glycolysis and pentose phosphate pathway was done. The dose-dependent inhibitory effect of ethanol on activity of limiting enzymes of these metabolic ways, as well as anaerobic reorientation of glucose metabolism was recognised with the increase of the dose of the intake alcohol. Morfine (10 mg/kg) activated enymes of glycolysis and pentose phosphate pathway, but in contrast to ethanol it did not influence these parameters at the dose 20 or 40 mg/kg.

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