Genetic development of an inbred rat strain with increased resistance adaptation to a hot environment

Abstract

The purpose of this study was to demonstrate resistance adaptation based on genotypic adaptation and to develop an inbred rat strain with genotypic resistance adaptation to a hot environment. Survival time (ST) at an ambient temperature (Ta) of 42.5 degrees C was determined without appreciable thermal damage. Rats with the longest ST were sibmated over 30 generations and designated FOK. The ST, evaporative water loss, and body water economy increased rapidly during the first 10-15 generations, followed by a more gradual increase. The FOK rat resisted a Ta of 42.5 degrees C for > 5 h; this ability was hereditary. Body size progressively decreased during the early generations. The ST was longer (P < 0.01) and evaporative water loss was significantly higher (P < 0.01) in the FOK rat compared with three other strains. Tail lengths in the FOK rat were slightly shorter than those of three controls (P < 0.01). The heat loss system in the FOK rat may depend on the ability to mobilize and evaporate body fluids efficiently. FOK rats can be used for phenotypic comparisons with other strains, as well as in molecular genetic studies on thermoregulation, osmoregulation, and resistance adaptation to heat using recombinant inbred and recombinant congenic lines.

Water relations of tetrapod integument

“…Water barrier function in amniotes appears to be relatively fixed and characteristic of species, and the heritability of TEWL has been demonstrated in mammals (Furuyama and Ohara, 1993). However, the capacity of animals to adjust R s when environmental conditions change is also an important aspect of adaptation, including phenotypic plasticity, acclimatization and developmental plasticity.…”

Phenotypic flexibility in cutaneous water loss and lipids of the stratum corneum

“…We know that the magnitude of TEWL is a heritable trait, at least in mammals (Furuyama and Ohara, 1993), and, by inference, we assume that rates of CWL are influenced by heritable factors. Hence, it could be that phenotypes with a stronger barrier to water vapor diffusion have been selected in deserts.…”

Heat Production by Brown Adipocytes of FOK Rats Genetically Resistant to a Hot Environment.

“…For example, heat-acclimated mice [13], hamsters [2,4], and rats [21] have been reported to have lower whole body-oxygen consumption than nonacclimated controls. FOK rats were established as an inbred strain with genotypic adaptation to a hot environment, showing a long survival time at an ambient temperature of 42.5°C [6]. The mechanism of the heat resistance of this animal has not been well documented except for a description of high water loss by evaporation [6].…”

“…FOK rats were established as an inbred strain with genotypic adaptation to a hot environment, showing a long survival time at an ambient temperature of 42.5°C [6]. The mechanism of the heat resistance of this animal has not been well documented except for a description of high water loss by evaporation [6].…”

“…The rats used in the present study were FOK/Ncu (FOK), developed by Furuyama and Ohara [6]. WKAH/HkmSlc (Wistar King Albino Hokkaido, WKAH) rats, used as a control, were purchased from Japan SLC Co.…”