Rhythmic cortisol secretion in the equine: Analysis and physiological mechanisms
作者:
J. W. Evans,
C. M. Winget,
E. J. Pollak,
期刊:
Journal of Interdisciplinary Cycle Research
(Taylor Available online 1977)
卷期:
Volume 8,
issue 2
页码: 111-121
ISSN:0022-1945
年代: 1977
DOI:10.1080/09291017709359550
出版商: Taylor & Francis Group
关键词: Circadian rhythms;control rhythms;equine cortisol rhythms;ultradian rhythms
数据来源: Taylor
摘要:
Four Thoroughbred mares (no. 1–4) were maintained under constant temperature (24°C) and controlled light (L/D:12/12 with lights on at 06.00 hr) conditions. They were fed and watered ad libitum with fresh feed and water given at 09.00 hr. After a 45‐day pre‐conditioning period, blood samples were obtained by veinipuncture at 4‐hr intervals for 14 days to determine circadian and day‐to‐day variation. The horses exhibited a circadian rhythm with maximum values attained at about 12.00 hr, however, there are periods of days in which no rhythm is distinguishable. Ultradian rhythms with mean periods of 105 to 128 and 24 to 31 min are superimposed upon the circadian rhythm. The individual rhythms are quite variable from horse to horse and within the same horse. During periods of decline in plasma cortisol with metabolic half‐lives of approximately 70 min, secretion of cortisol was very low or had ceased. During periods of increasing plasma concentration, secretion was occurring at a faster rate than degradation. Rapid decreases in plasma concentration (metabolic half‐life of approximately 30 min) was accompanied by a rise in specific activity indicating cortisol with a high specific activity was entering the plasma pool from other storage pools.
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