Carbohydrate and Lipid Metabolism

Lindsay, D. B.; Leat, W. M. F.

doi:10.1007/978-3-642-66115-0_3

Cited by 22 publications

(8 citation statements)

References 90 publications

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“…This may be because in sheep, the red cells are relatively impermeable to glucose, and thus plasma glucose levels are higher than whole-blood glucose levels [34] . Since glucose in the interstitial space has diffused across the endothelium from the plasma, this higher plasma level may account for the slightly higher interstitial glucose level that we observed.…”

Section: Discussionmentioning

confidence: 96%

Cot-Side Electro-Encephalography and Interstitial Glucose Monitoring during Insulin-Induced Hypoglycaemia in Newborn Lambs

Harris¹,

Battin

Williams

et al. 2008

Neonatology

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Background: The optimal approach to detection and management of neonatal hypoglycaemia remains unclear. Objectives: We sought to demonstrate whether electro-encephalography (EEG) changes could be detected on the amplitude-integrated EEG monitor during induced hypoglycaemia in newborn lambs, and also to determine the accuracy of continuously measured interstitial glucose in this situation. Methods: Needle electrodes were placed in the P3-P4, O1-O2 montages. The interstitial glucose sensor was placed subcutaneously. After 30 min baseline recordings, hypoglycaemia was induced by insulin infusion and blood glucose levels were monitored every 5 min. The infusion was adjusted to reduce blood glucose levels by 0.5 mmol/l every 15 min and then maintain a blood glucose level <1.0 mmol/l for 4 h. EEG parameters analysed included amplitude, continuity and spectral edge frequency. The interstitial and blood glucose levels were compared. Results: All lambs (n = 15, aged 3–11 days) became hypoglycaemic, with median blood glucose levels falling from 6.5 to 1.0 mmol/l, p < 0.0001. There were no detectable changes in any of the measured EEG parameters related to hypoglycaemia, although seizures occurred in 2 lambs. There was moderate agreement between the intermittent blood glucose and continuous interstitial glucose measurements in the baseline, decline, and hypoglycaemia periods (mean difference –0.7 mmol/l, 95% confidence interval, CI, –2.8 to 1.4 mmol/l). However, agreement was poor during reversal of hypoglycaemia (mean difference 4.5 mmol/l, 95% CI –1.1 to 10.7 mmol/l). Conclusions: The cot-side EEG may not be a useful clinical tool in the detection of neurological changes induced by hypoglycaemia. However, continuous interstitial glucose monitoring may be useful in the management of babies at risk of hypoglycaemia.

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Section: Discussionmentioning

confidence: 96%

Cot-Side Electro-Encephalography and Interstitial Glucose Monitoring during Insulin-Induced Hypoglycaemia in Newborn Lambs

Harris¹,

Battin

Williams

et al. 2008

Neonatology

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“…Although washing and storage of erythrocytes decreased the rate of DHT reduction by about 90%, the 20-fold dilution of plasma glucose in the standard assay did not result in lower measured rates. Glucose added to simulate physiological concentrations did not increase v. Thus in vivo or in vitro variations below the normal adult plasma glucose concentrations of 3-6 mmol I-I (Lindsay and Leat 1975) would not limit the activity of HSD's in erythrocytes. This was not so for human blood as glucose increased 17iJ-HSD activity markedly in vitro (Mig eon et al 1962).…”

Section: Discussionmentioning

confidence: 88%

“…The fact that lysed erythrocytes from two sheep regained 160-200% of their original activities in the presence of NADPH, in contrast to the 56% of 20a-HSD activity regained in lysed fetal cells (Nancarrow et al 1984), suggests that the maximum activity of 3a-and 3iJ-HSD is restricted not by plasma glucose concentrations, but by the relative impermeability of adult blood cells to glucose (Widdas 1961). Fetal erythrocytes maintain an intracellular concentration of glucose about twice that of the plasma (Lindsay and Leat 1975). Despite the suggestions by Widdas (1961) that sufficient glucose could still enter adult cells to maintain the metabolic profiles and by Nancarrow et al (1984) that the restricted entry of glucose is not responsible for the periparturient decline in 20a-HSD activity, the possibility remains that endogenous NADPH production in adult erythrocytes is limited by factors regulating glucose entry or metabolism.…”

Section: Discussionmentioning

confidence: 97%

Adult Sheep Blood Metabolizes Dihydrotestosterone to 5a-Androstane-3 a,17ß-diol and 5a -Androstane-3 ß, 17ß-diol

Nancarrow

Connell²

1987

Aust. Jnl. Of Bio. Sci.

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The metabolism of 5a-dihydrotestosterone by adult sheep blood was investigated. Erythrocytes contain 3a-and 3i1-hydroxysteroid dehydrogenase activities. The mean rate of reduction of 5a-dihydrotestosterone by erythrocytes established in 15-min incubations was 0·66 ± 0·36 (s.d.) I'mol ml-1 erythrocytes h -1 and at equilibrium after a 60-min incubation, 90·6 ± 5· I % of the substrate was reduced. The reduction of 5a-dihydrotestosterone was shown to be dependent upon extracellular glucose and the intracellular cofactor NADPH. The proportion of the two reduction products was determined at equilibrium after separation by paper partition. chromatography and favoured 5a-androstane-3a, 17i1-diol (96·0%) to 5a-androstane-3i1,17i1-diol (4 ·0%). The identities and proportions of the two products were confirmed by recrystallization procedures.The fact that erythrocytes can significantly metabolize the androgen 5a-dihydrotestosterone is evidence for the recognition of blood as a major component of steroid endocrine homeostasis in sheep.

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“…At the same time, glucose concentrations in the plasma of the fetus are normally maintained at around 1 mmol/1 despite quite wide daily fluctuations (Comline & Silver, 1970;Shelley, 1973). These concentrations are maintained at about 25% of adult levels (Comline & Silver, 1970;Shelley, 1973;Bassett & Madill, 1974;Lindsay & Leat, 1975). It is also known that while glucose enjoys a facilitated entry into fetal erythrocytes (Widdas, 1955), adult cells virtually exclude the hexose (Widdas, 1961).…”

Section: Introductionmentioning

confidence: 96%

Relationship between glucose and 20α-hydroxysteroid dehydrogenase in fetal sheep erythrocytes

Nancarrow¹,

Connell²,

Stevens³

1984

Journal of Endocrinology

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We have examined whether glucose supply to fetal sheep erythrocytes limits the rate of 20 alpha-reduction of progesterone in blood and as such is associated with the progressive loss of 20 alpha-hydroxysteroid dehydrogenase activity which has been observed from 30 days before term. Enzyme activity in erythrocytes depleted of glucose by washing was regained in the presence of at least 0.167 mmol glucose/1. The cofactor NADPH was necessary to support the reaction in lysed cells. Addition of glucose to whole blood diluted 20-fold for assay of 20 alpha-hydroxysteroid dehydrogenase did not increase the rate of reaction. Infusion of dextrose to increase fetal plasma glucose concentrations had no effect on 20 alpha-hydroxysteroid dehydrogenase activity. Over the period from 114 to 137 days of gestation, both dextrose- and saline-infused fetuses showed a decline in enzyme activity from a combined mean of 1.45 +/- 0.21 (S.E.M.) to a mean of 0.78 +/- 0.18 mumol/ml erythrocytes per h. Fetal leucocytes did not contribute significantly to the activity of 20 alpha-hydroxysteroid dehydrogenase in whole blood. The rate of 20 alpha-reduction of progesterone in the blood of eight fetuses with indwelling carotid catheters declined from 2.31 +/- 0.09 mumol/ml erythrocytes per h at 90-95 days of gestation to 0.73 +/- 0.04 mumol/ml per h at 141-145 days. However, a consistent decline was only observed after 116-120 days. The apparent equilibrium position for progesterone reduction to 20 alpha-dihydroprogesterone varied between 83.9 +/- 1.8 and 65.7 +/- 4.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

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Carbohydrate and Lipid Metabolism

Cited by 22 publications

References 90 publications

Cot-Side Electro-Encephalography and Interstitial Glucose Monitoring during Insulin-Induced Hypoglycaemia in Newborn Lambs

Cot-Side Electro-Encephalography and Interstitial Glucose Monitoring during Insulin-Induced Hypoglycaemia in Newborn Lambs

Adult Sheep Blood Metabolizes Dihydrotestosterone to 5a-Androstane-3 a,17ß-diol and 5a -Androstane-3 ß, 17ß-diol

Relationship between glucose and 20α-hydroxysteroid dehydrogenase in fetal sheep erythrocytes

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