Original Research

Circadian secretion patterns of ß-endorphin and leucine enkephalin

E. H. de Wet, J. M. C. Oosthuizen
Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie | Vol 11, No 1 | a516 | DOI: https://doi.org/10.4102/satnt.v11i1.516 | © 1992 E. H. de Wet, J. M. C. Oosthuizen | This work is licensed under CC Attribution 4.0
Submitted: 08 July 1992 | Published: 08 July 1992

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E. H. de Wet,, South Africa
J. M. C. Oosthuizen,, South Africa

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Abstract

ß-endorphin and leucine enkephalin are neuropeptides with potent opioid activity. In a study to investigate the circadian secretion patterns of the above-mentioned, blood samples were collected hourly from 12 healthy males who were subjected to the experiment for 24 hours. Radioimmunoassays were used in the analysis of plasma samples for ß-endorphin and leucine enkephalin. Peak concentrations of ß-endorphin were demonstrated from 08:00-09:00, while peak concentrations of leucine enkephalin occured from 23:00-07:00. Trough concentrations of ß-endorphin occurred from 24:00-05:00, while trough con­centrations of leucine enkephalin were demonstrated from 09:00-12:00. The illustrated circadian secretion pattern for ß-endorphin simulates the well-known circadian rhythm of cortisol. The answer to this may be in the fact that ß-endorphin and corticotropin stem from the same precursor. The illustrated circadian secretion pattern for leucine enkephalin simulates that of melatonin. The reason for this is unclear.

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