Binding and clearance of radioactive adrenaline and noradrenaline in sheep blood

Veterinary Research Communications
S M El-BahrR G Palme

Abstract

An understanding of the conditions influencing protein binding of catecholamines (CAs) is important in studying their metabolic effects. Unfortunately, reports on plasma protein binding of CAs are scarce, conflicting and mainly performed in vitro. The aim of our in vivo and in vitro studies was to investigate binding and clearance of radioactive adrenaline (epinephrine) ((3)H-A), noradrenaline (norepinephrine) ((3)H-NA) and their metabolites in sheep blood. The time course of the radioactivity in the blood after intravenous injection of (3)H-A and (3)H-NA (3.7 MBq each) in 4 sheep (2 of each sex; total of 8 administrations) was determined. Blood samples were taken from the jugular vein. The highest radioactivity was observed in the first sample (5 min) following injection. Radioactivity showed a biphasic disappearance. An initial stage, in which radioactivity decreased rapidly (within 1 h) after the injection, was followed by a slow stage, lasting for up to 1 month, until background levels were reached. In vitro results indicated that NA and A were present not only in plasma (70%) but also in the erythrocytes (30%; mainly bound to haemoglobin). Sephadex G-25 gel filtration revealed that from the plasma fraction about 15% was st...Continue Reading

References

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Citations

Feb 16, 2008·Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology·M LepschyR G Palme
Jul 12, 2011·British Journal of Pharmacology·Mansoor N BangashRupert M Pearse

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