Jan 01 1999 - Physiology Web Site

Hormonol Relations in Autoregulatory Thermoregulation During Flight in Birds

J. Anim. Morph. Physiol., Vol. 46, Nos. 1 & 2, pp 71 to 76, 1999

By J.C. George
Department of Zoology , University of Guelph, Guelph, Ontario, Canada N1G 2W1
Fax: (519) 767-1656; email: jgeorge@uoguelph.ca

Dedicated to the memory of the Late Rajini Nene ( Dept. of Zoology, M.S. University of Baroda, baroda), former student, Co-author and colleague, for her seminal contributions to the studies in muscle structure and function.

ABSTRACT

In birds, prolonged flight could produce hypoerthermia which in turn lead to heat stroke, unless prevented by increased rate of heat-loss from the body and the brain supplied with cooler blood. The present review is based on data obtained from the several studies with homing pigeons on the circulating levels of certain hormones after a 48 km free flight. Providing evidence for the existence of an autoregulatory mechanism for the mainstream of homeostatis. Flight-induced increase in circulating levels of arginine vasotocin is indicative of the role of this hormone in thermoregulation as well as water conservation. Increase in the levels of melatonin ensures not only the prevention of flight-induced hyperthermia and the threat of heat stroke but also the reduction of stress and the supply of cooler blood to the brain. However, during extended and exhaustive flight, the process of thermoregulation is further enhanced by significantly reducing the levels of thyroxine (T4) and triiodothyronine (T3) while increasing the levels of reverese T3, the inactive form of T3.C

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