Effects of insulin on glucose turnover rates in vivo: Isotope dilution versus constant specific activity technique

In vivo studies on the glucose system often require its perturbation by an exogenous input of glucose, whereas glucose turnover is assessed by infusing a glucose tracer. The constant infusion represents the usual format of tracer administration, but it has no clear advantage other than simplicity. Here we propose a different tracer infusion format. It consists of infusing the tracer in parallel with unlabeled glucose so as to maintain a constant specific activity in the infusate. This protocol does not increase experimental complexity and provides new information on the glucose system in non-steady state by allowing reconstruction of the endogenous component of glucose concentration. This reconstruction only requires very general assumptions, such as tracer-tracee indistinguishability and mass conservation; in particular it is independent of the glucose model structure, i.e., number of compartments and their interconnections. A proof of the result is given for a general nonlinear model of the glucose system. The constant specific activity input is also advantageous for non-steady-state calculations, because it reduces the variation in the measured plasma glucose specific activity. The glucose system has served as the prototype, but the protocol is applicable to other blood-borne substances. The radioactive tracer case has been considered, but the same results apply to stable isotope tracers as well; in this case they also become relevant in a somewhat different context, i.e., kinetic studies in steady state.

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Use of [3-3H]glucose and [6-14C]glucose to measure glucose turnover and glucose metabolism in humans

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.263.1.e17 ◽

1992 ◽

Vol 263 (1) ◽

pp. E17-E22 ◽

Cited By ~ 2

Author(s):

H. Katz ◽

M. Homan ◽

P. Butler ◽

R. Rizza

Keyword(s):

Indirect Calorimetry ◽

Glucose Oxidation ◽

Insulin Infusion ◽

Specific Activity ◽

Glucose Turnover ◽

Detectable Effect ◽

High Dose ◽

Turnover Rates ◽

Extracellular Glucose ◽

Total Glucose

[3-3H]glucose is frequently used to measure glucose turnover in humans. If fructose 6-phosphate-fructose 1,6-diphosphate cycling (Fpc) is negligible in both liver and muscle, then [3-3H]- and [6-14C]glucose (corrected for Cori cycle activity) should provide equivalent measures of glucose turnover. In addition, if glycogenolysis is fully suppressed, then [14C]lactate specific activity should equal that of [6-14C]glucose from which it was derived, and oxidation of [6-14C]glucose, as measured by rate of generation of 14CO2, should equal total glucose oxidation (i.e., that derived from intra- and extracellular pools) as measured by indirect calorimetry. To address these questions, glucose turnover was measured simultaneously with [3-3H]- and [6-14C]glucose in the basal state and in presence of low (approximately 200 pM) and high (approximately 750 pM) insulin concentrations. Glucose turnover rates measured with [3-3H]- and [6-14C]glucose were equivalent at all insulin concentrations, indicating that Fpc had no detectable effect on measurement of glucose appearance. [14C]lactate specific activity was lower (P less than 0.01) than that of [6-14C]glucose in the basal state but not during either low- or high-dose insulin infusion, implying that all lactate was derived from extracellular glucose. On the other hand, glucose oxidation as measured by rate of generation of 14CO2 was lower (P less than 0.05) than glucose oxidation as measured by indirect calorimetry during both insulin infusions, implying either that suppression of glycogenolysis was not complete in all tissues or that one or both of these techniques do not accurately measure glucose oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

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A New Technic for the Production of an in Vivo Labeled Fibrinogen

Blood ◽

10.1182/blood.v29.4.517.517 ◽

1967 ◽

Vol 29 (4) ◽

pp. 517-525 ◽

Cited By ~ 3

Author(s):

HENRY GANS ◽

JAMES MC LEOD ◽

JAMES T. LOWMAN

Keyword(s):

Amino Acid ◽

Specific Activity ◽

High Specific Activity ◽

Entire Period ◽

Turnover Rates ◽

Prolonged Infusion ◽

Slow Infusion

Abstract The fact that in vitro labeled proteins, as a rule, exhibit faster turnover rates than in vivo labeled materials led us to explore means of obtaining in vivo labeled fibrinogen of high specific activity. It was found that defibrination of the rat provides a stimulus for the liver to regenerate fibrinogen at an accelerated rate. Administration of seleno75 methionine shortly after thrombin-induced defibrination of the animal resulted in the incorporation of large quantities of the label. The rate of incorporation was further increased if the amino acid was administered as a slow infusion during the entire period of fibrinogen regeneration. In addition, prior nephrectomy of the animal would appear to result in a slight increase in specific activity of the fibrinogen preparation obtained. The results of these studies indicate that defibrination, nephrectomy, and the prolonged infusion of the labeled amino acid selenomethionine provided us with a technic for obtaining a biosynthetically labeled, γ-emitting, fibrinogen preparation of high specific activity.

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Metabolism of glucose in hyper- and hypo-thyroid rats in vivo. Relation of catecholamine actions to thyroid activity in controlling glucose turnover

Biochemical Journal ◽

10.1042/bj1820585 ◽

1979 ◽

Vol 182 (2) ◽

pp. 585-592 ◽

Cited By ~ 13

Author(s):

F Okajima ◽

M Ui

Keyword(s):

Hepatic Glucose Production ◽

Glucose Production ◽

Rate Coefficients ◽

Glucose Turnover ◽

Turnover Rates ◽

Beta Adrenergic ◽

Thyroid State ◽

Adrenergic Antagonist ◽

6 Hydroxydopamine

1. In euthyroid rats, treatment with reserpine of 6-hydroxydopamine, which deprived neuronal terminals of catecholamines, resulted in increases in rates and rate coefficients for blood glucose turnover in the starved states as determined by decay of [U-14C,6-3H]-glucose. Conversely, the injection of adrenaline or noradrenaline into starved euthyroid rats caused a marked decrease in rate coeeficients for glucose turnover. There was no change in the percentage glucose recycling under these conditions. 2. Adrenaline and noradrenaline caused more pronounced hyperglycaemia in hyperthyroid than in euthyroid rats owing to the greater activation of hepatic glucose production. 3. The increase in glucose turnover characteristics of hyperthyroidism was observed even after treatment with an alpha- or beta-adrenergic antagonist, showing the insignificant role of the balance between alpha- and beta-adrenergic receptors in the thyroid-dependent metabolic changes. 4. Rate coefficients for glucose turnover were not affected by reserpine treatment or catecholamine injections when rats had been rendered hyperthyroid. 5. Thus catecholamines are direct determinants of glucose-turnover rates in the starved state, and depend to some extent on the prevailing thyroid state.

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GLUCOCORTICOID SYNTHESIS FROM PREGNENOLONE BY SHEEP FOETAL ADRENALS IN VITRO

Journal of Endocrinology ◽

10.1677/joe.0.0580485 ◽

1973 ◽

Vol 58 (3) ◽

pp. 485-491 ◽

Cited By ~ 9

Author(s):

I. J. DAVIES ◽

K. J. RYAN

Keyword(s):

Isotope Dilution ◽

Adrenal Glands ◽

Specific Activity ◽

Newborn Period ◽

Adult Sheep ◽

Age Related ◽

Period Of Gestation ◽

Constant Specific Activity

SUMMARY [7-3H]Pregnenolone was incubated with homogenates of adrenal glands from two 100-day-old sheep foetuses. Cortisol and corticosterone were isolated and identified by reverse isotope dilution and recrystallization to constant specific activity. Together these two compounds accounted for 12% and 17% of the substrate with the two tissue preparations. Other C21 and C19 metabolites which were sought were not present in appreciable quantities. Additional incubations were done with the adrenals of lamb foetuses ranging in age from 110 days of gestation to the immediate newborn period. Glucocorticoidogenic capacity similar to that of the 100-day-old foetuses was demonstrated throughout this period and no age-related change was evident. These results demonstrate that the lamb foetal adrenal has a substantial enzymic capacity for glucocorticoid synthesis throughout at least the last third of gestation. In conjunction with the observations of others, these experiments support the hypothesis that during this period of gestation the lamb foetal adrenal is actively synthesizing glucocorticoids in a manner which is similar to the lamb at term and the adult sheep.

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Mutations That Confer Resistance to 2-Deoxyglucose Reduce the Specific Activity of Hexokinase from Myxococcus xanthus

Journal of Bacteriology ◽

10.1128/jb.181.7.2225-2235.1999 ◽

1999 ◽

Vol 181 (7) ◽

pp. 2225-2235 ◽

Cited By ~ 10

Author(s):

Philip Youderian ◽

Matthew C. Lawes ◽

Chad Creighton ◽

Jessica C. Cook ◽

Milton H. Saier

Keyword(s):

Specific Activity ◽

Myxococcus Xanthus ◽

Glucose Turnover ◽

Enzyme Assays ◽

Phosphotransferase System ◽

Glucokinase Gene ◽

Multicellular Development ◽

Spontaneous Frequency

ABSTRACT The glucose analog 2-deoxyglucose (2dGlc) inhibits the growth and multicellular development of Myxococcus xanthus. Mutants ofM. xanthus resistant to 2dGlc, designated hexmutants, arise at a low spontaneous frequency. Expression of theEscherichia coli glk (glucokinase) gene in M. xanthus hex mutants restores 2dGlc sensitivity, suggesting that these mutants arise upon the loss of a soluble hexokinase function that phosphorylates 2dGlc to form the toxic intermediate, 2-deoxyglucose-6-phosphate. Enzyme assays of M. xanthusextracts reveal a soluble hexokinase (ATP:d-hexose-6-phosphotransferase; EC 2.7.1.1 ) activity but no phosphotransferase system activities. The hexmutants have lower levels of hexokinase activities than the wild type, and the levels of hexokinase activity exhibited by the hexmutants are inversely correlated with the ability of 2dGlc to inhibit their growth and sporulation. Both 2dGlc andN-acetylglucosamine act as inhibitors of glucose turnover by the M. xanthus hexokinase in vitro, consistent with the finding that glucose and N-acetylglucosamine can antagonize the toxic effects of 2dGlc in vivo.

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DETECTION OF [3H]5α-ANDROSTANE-3α,17β-DIOL AND [3H]17β-HYDROXY-5α-ANDROSTAN-3-ONE IN MOUSE TESTES FOLLOWING ADMINISTRATION OF [3H]TESTOSTERONE

Acta Endocrinologica ◽

10.1530/acta.0.0740177 ◽

1973 ◽

Vol 74 (1) ◽

pp. 177-185 ◽

Cited By ~ 2

Author(s):

Hisanori Kasai ◽

Shutaro Mizutani ◽

Keishi Matsumoto

Keyword(s):

Seminal Vesicle ◽

Isotope Dilution ◽

Specific Activity ◽

Constant Specific Activity

ABSTRACT [3H]Testosterone (2.0 μg/300 μCi or 3.3 μg/500 μCi) was injected into each of 23 mice, aged 45 days and the distribution of tritium among certain unconjugated steroids in the whole tissue, nuclear, mitochondrial + microsomal and cytosol fractions from the testes, liver, muscle, blood and prostate + seminal vesicle was determined 1 h after the injection. [3H] 17β-Hydroxy-5α-androstan-3-one could be clearly shown in the whole tissue and the three fractions from the testes and prostate-seminal vesicle, but none was identified in any of the fractions from androgen-unresponsive tissues such as the liver, muscle and blood. However, the levels of [3H] 17β-hydroxy-5α-androstan-3-one were much higher in the prostate-seminal vesicle than in the testes. The levels of [3H]5α-androstane-3α,17β-diol in all the fractions from the testes as well as those from the prostate-seminal vesicle were in the order of ten times the levels in the corresponding fractions from the liver and muscle. Identification of [3H] steroids was accomplished by reverse isotope dilution and re-crystallization to constant specific activity. It would appear that the mouse testes belong to androgen-responsive tissues and that 5α-androstane-3α,17β-diol and 17β-hydroxy-5α-androstan-3-one may play a role in the testes.

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The Action of Pitressin on Solute Permeability of the Rabbit Nephron in Vivo

The Journal of General Physiology ◽

10.1085/jgp.50.1.1 ◽

1966 ◽

Vol 50 (1) ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

E. C. Foulkes

Keyword(s):

Specific Activity ◽

Specific Effect ◽

Renal Medulla ◽

Urine Flow ◽

Intraarterial Infusion ◽

Plasma Urea ◽

Solute Permeability ◽

Isotopic Equilibration ◽

Constant Specific Activity

The isotopic equilibration of urea, thiourea, and inulin between urine and plasma was determined in rabbits in the presence or absence of antidiuretic hormone (ADH). Animals were anesthetized with ethanol and permitted to reach steady state after completion of surgery. Tracer was then administered by intraarterial infusion in such a manner that a high constant specific activity in plasma was rapidly attained. Urine flow was kept independent of ADH by addition of mannitol. Urea/creatinine clearance ratios and the accumulation of urea in renal medulla and papilla also remained unaffected by ADH. Under these conditions, thiourea and inulin at all times approached equilibrium, at similar rates. In the absence of ADH, urea also equilibrated at a rate similar to that of inulin. The addition of ADH, however, significantly prolonged the delay before urinary urea reached the high constant specific activity of plasma urea. These observations are interpreted in terms of a specific effect of the hormone on the solute permeability of the nephron.

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Conversion in vivo of injected estradiol-17β-4-14C and estrone-4-14C to urinary estradiol-17α-14C by the hen

Canadian Journal of Biochemistry ◽

10.1139/o68-144 ◽

1968 ◽

Vol 46 (8) ◽

pp. 965-970 ◽

Cited By ~ 6

Author(s):

Shree Mulay ◽

R. H. Common

Keyword(s):

Thin Layer ◽

Ad Hoc ◽

Specific Activity ◽

Urinary Steroid ◽

Estradiol 17Β ◽

Steroid Estrogens ◽

Constant Specific Activity

Radioactive estradiol-17α was identified in urine of hens that had received injections of estradiol-4-14C, or of estrone-4-14C, or of a mixture thereof. Identification was based on thin-layer chromatographic mobilities of the phenol and three derivatives, and by recrystallization of the phenol and of its diacetate in admixture with appropriate carrier to constant specific activity. The possibility of microbiological formation of the radioactive estradiol-17α after excretion of the urine was excluded by ad hoc experimentation. The results are advanced in support of the view that estradiol-17α is one of the normal urinary steroid estrogens of the fowl.

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Biogenetic mechanisms. I. Incorporation of 4-14C-progesterone into gitoxigenin by Digitalis purpurea

Canadian Journal of Biochemistry ◽

10.1139/o70-037 ◽

1970 ◽

Vol 48 (2) ◽

pp. 216-218 ◽

Cited By ~ 7

Author(s):

Liat Tan

Keyword(s):

Gas Chromatography ◽

Infrared Spectroscopy ◽

Thin Layer ◽

Isotope Dilution ◽

Specific Activity ◽

Carrier Material ◽

Digitalis Purpurea ◽

In Vivo Administration ◽

Active Precursor

In vivo administration of 4-14C-progesterone to a 6-month-old Digitalis purpurea species over a period of 4 weeks resulted in 0.477% incorporation of the radioactivity into gitoxigenin. The identity of the crystalline cardenolide isolated was established by thin-layer and gas chromatography, infrared spectroscopy, as well as isotope dilution with authentic carrier material and crystallization to constant specific activity. The role which progesterone may play as an active precursor in the biogenesis of steroid cardenolides is discussed.

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