Thermoregulatory responses to acute heat loads in the FOK rat |
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Authors: | N Sugimoto O Shido F Furuyama S Sakurada H Nishino |
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Institution: | Department of Physiology, School of Medicine, Faculty of Medicine, Kanazawa University, Japan. ns@med.kanazawa-u.ac.jp |
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Abstract: | FOK is an inbred rat strain with a genotypic adaptation to hot environments. The present study investigated the mechanism
of the high heat tolerance of the FOK rat. Male FOK and WKAH rats were used. They were loosely restrained and placed individually
in a direct calorimeter with an ambient temperature of 24°C. Their hypothalamic temperature, evaporative and nonevaporative
heat loss and heat production were measured. After thermal equilibrium had been attained, the rats were warmed for 30 min
with a chronically implanted intraperitoneal electric heater(internal heating). At least 90 min after the heating, the jacket
water temperature surrounding the calorimeter chamber was gradually raised from 24°C to 36°C in 80 min (external warming).
During the internal heating, changes in the thermoregulatory parameters did not differ between the groups. During the external
warming, the evaporative heat loss of the FOK rat was significantly greater than that of the WKAH rat, while changes in nonevaporative
heat loss and heat production did not differ between the groups. The results suggest that in the FOK rat, the improved heat
tolerance is attributable to an enhanced evaporative heat loss response, but not to a facilitation of nonevaporative heat
loss or of metabolic depression.
Received: 8 March 1999 / Accepted: 14 July 1999 |
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Keywords: | Evaporative and nonevaporative heat loss Heat production FOK rat WKAH rat Heat tolerance |
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