Plasma cortisol in cattle: Circadian rhythm and exposure to a simulated high altitude of 5,000 m |
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Authors: | F. L. Hays H. Armbruster W. Vetter W. Bianca |
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Affiliation: | (1) Laboratorium für Bioklimatologie am Institut für Tierzucht, Eidgenössische Technische Hochschule, Universitätstrasse 2, 8006 Zürich, Switzerland;(2) Department für Innere Medizin der Universität, Kantonsspital, Rämistrasse 100, 8006 Zürich, Switzerland |
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Abstract: | After a 2 week control period at 400 m, cattle were exposed to 5,000 m simulated altitude for 2 weeks, which was followed by a 2-week post-altitude control period. Plasma cortisol values from blood samples taken every 30 min for a total of 24 h indicated that cortisol was secreted episodically and that a circadian rhythm existed. When cortisol values were grouped into 4, 6-h periods, plasma cortisol was most abundant from 06:00 to 12:00 h with an average of 0.96µ g/100 ml and least abundant from 00:30 to 06:00 h with an average of 0.55µ g/100 ml. Plasma cortisol increased from 0.42 to 3.08µ g/100 ml during the 4 h ascent to 5,000 m and decreased to near normal levels the following day. A rhythmic plasma cortisol pattern was maintained after one day at simulated high altitude. |
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