Erythropoietin does not demonstrate circadian rhythm in healthy
males .
Roberts, D., D. J. Smith.
Faculty of Kinesiology, University of Calgary, Calgary, Alberta,
CANADA T2N 1N4, Phone: (403) 220-4736, Fax: (403) 284-3553, e-mail
address: delia@kines.ucalgary.ca
APStracts 2:0478A, 1995.
The hormone erythropoietin (Epo) produced in the kidneys in response
to hypoxia stimulates the production of red blood cells. We measured
serum Epo levels in 26 healthy males over a 24 hr period in order to
determine if Epo is secreted according to a circadian rhythm. Samples
were collected every 2 to 4 hrs, Epo was measured using a
radioimmunoassay (INCSTAR Epo-trac). To determine if blood collection
had any effect on Epo production one half of the subjects began the
collection period in the morning and the other half in the evening.
Exercise and the use of prostaglandin inhibitors were prohibited to
eliminate fluctuations in Epo production in response to discrete
stimuli. The daily mean+/-SD Epo concentration for all subjects
combined was 15.5+/-5.3 U/L. No significant circadian variation in
serum Epo concentrations was observed in either group, or when both
groups were combined; however, a measure of individual variance was
observed, (mean squared deviation = 0.8 +/- 0.4).
Received 20 June 1995; accepted in final form 25 October 1995.
APS Manuscript Number A660-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95