Reach further, in an Open Access Journal Endocrinology, Diabetes & Metabolism Case Reports

ISSN 1470-3947 (print)
ISSN 1479-6848 (online)

Searchable abstracts of presentations at key conferences in endocrinology

Published by BioScientifica
Endocrine Abstracts (2007) 14 P47 

Competition between catecholamines and glucose for binding sites on proteins of erythrocytes

Michael Lepschy, Erich Moestl & Rupert Palme

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Glucose is slowly linked to haemoglobin in a non-enzymatic reaction and the determination of a glycated protein (HbA1c) is used for long term monitoring blood glucose concentrations. Radiometabolism studies in sheep showed that a haemoglobin-adduct formation also takes place with epinephrine or norepinephrine.

The aim of our study was to elucidate if there is a competition between catecholamines and glucose for binding sites on proteins of the erythrocytes.

Heparinised canine blood was obtained and centrifuged at 1500 g and the cells were washed three times with isotonic NaCl-solution. Afterwards, 5 portions of erythrocytes (0.7 ml each) were re-suspended in 7 ml TCM ‘Eagle’ and incubated with epinephrine and norepinephrine (1 and 10 ng/ml) for 3 days at 38.6 °C. One portion served as control.

Afterwards the erythrocyte portions were split into sub-samples of 0.2 ml each. One half was incubated with 3H-norepinephrine for 1 h (unhaemolysed), the second half with 14C-glucose for 10 days after haemolysis by freezing. To determine the uptake of 3H-norepinephrine, samples were centrifuged and the radioactivity of the supernatant was measured. In total 410±7 Bq of the added 574±16 Bq were measured in the control samples, whereas all groups preincubated with non-radioactive catecholamines showed significantly (P<0.05) higher radioactivity. To determine the binding of 14C-glucose, proteins were precipitated. After centrifugation, 567±24 Bq of the added 1916±80 Bq were measured in the supernatant of the control samples. As in the experiment using 3H-norepinephrine, significant (P<0.05) higher values were measured in the supernatant of the preincubated erythrocytes, indicating a lower binding of 14C-glucose to the proteins.

Therefore we conclude that catecholamines are blocking binding sites on proteins of erythrocytes for additional adduct formation with 3H-norepinephrine or 14C-glucose.

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