Seasonal variation and the influence of body temperature on plasma concentrations and binding of thyroxine and triiodothyronine in the woodchuck

R A YoungE A Sims


Woodchuck plasma was collected during four seasons of the year and assayed for total and dialyzable (free) T4 and T3 and for rT3. Plasma concentrations of total and free T4 and T3 were higher in the spring (T4, 5.4 +/- 0.6 microgram/dl; free T4, 3.0 +/- 0.4 ng/dl; T3, 202 +/- 22 ng/dl; free T3, 0.51 +/- 0.04 ng/dl) and lower in the prehibernatory fattening period in summer (T4, 2.3 +/- 1.0 microgram/dl; free T4, 1.2 +/- 0.5 ng/dl; T3, 45 +/- 27 ng/dl; free T3, 0.16 +/- 0.10 ng/dl) and fall (T4, 3.2 +/- 1.0 microgram/dl; free T4, 1.3 +/- 0.2 ng/dl; T3, 130 +/- 12 ng/dl; free T3, 0.25 +/- 0.02 ng/dl). In spite of the extremely high concentrations of T3 in the winter (437 +/- 32 ng/dl), free T3 concentrations (0.034 +/- 0.003 ng/dl), when measured at the appropriate temperature for hibernation, were significantly lower than those found at other seasons of the year. Plasma binding of T3 was lower during the summer and increased again to approximately double the spring value during the winter. rT3 was at or below the sensitivity of the method (6 ng/dl) at all seasons. It is suggested that the wide seasonal variations in thyroid hormone concentrations and altered plasma protein binding may represent important adaptations influencing ...Continue Reading


Jul 20, 2010·Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology·Frank Scherbarth, Stephan Steinlechner
Jan 1, 1989·Pharmacology & Therapeutics·M J Fregly
Jan 1, 1983·Comparative Biochemistry and Physiology. A, Comparative Physiology·B A DemeneixN E Henderson
Jan 1, 1984·Comparative Biochemistry and Physiology. A, Comparative Physiology·M Jallageas, I Assenmacher
Jan 1, 1986·Comparative Biochemistry and Physiology. A, Comparative Physiology·E A Rickart
Jan 1, 1987·Comparative Biochemistry and Physiology. A, Comparative Physiology·A SeidelF Schulz
Jan 1, 1989·Comparative Biochemistry and Physiology. B, Comparative Biochemistry·N N BrustovetskyZ G Amerkhanov
Feb 19, 1998·Comparative Biochemistry and Physiology. Part C, Pharmacology, Toxicology & Endocrinology·K OhbaT Muraki
Jan 6, 2000·General and Comparative Endocrinology·Stewart C NicolT E Tomasi
Feb 1, 1986·General and Comparative Endocrinology·J G Eales, S Shostak
Feb 1, 1987·General and Comparative Endocrinology·J G Eales
Jun 1, 1983·General and Comparative Endocrinology·M Jallageas, I Assenmacher
Jan 6, 2004·American Journal of Physiology. Heart and Circulatory Physiology·Motoyuki IemitsuIwao Yamaguchi
May 12, 1998·The American Journal of Physiology·R E RawsonB C Tennant
May 10, 2017·Frontiers in Neuroscience·Stewart C Nicol
Aug 1, 1991·The American Journal of Physiology·J P Schröder-van der ElstJ Köhrle

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