Heat Stress Induces a Biphasic Thermoregulatory Response in Mice
Abstract
Previous animal models of heat stress have been compromised by methodologies such as restraint and anesthesia that confound our understanding of the core temperature (Tc) responses elicited by heat stress. Using biotelemetry, we developed a heat stress model to examine. Tc responses in conscious unrestrained C57BL/6J male mice. Prior to heat stress acclimated > 4 weeks to Ta of 25oC. Mice were exposed to ambient temperature (Ta) of 39.5+/- 0.2oC, in the absence of food and water, until they reached maximum Tc (Tc, Max) of 42.4 (N= 11), 42.7(N=12), or 43.OoC (N-11), defined as mild, moderate and extreme heat stress, respectively. Heat stress induced^13% BW loss that did not differ by final group Tc, whereas survival rate was affected by final Tc (100%) at 42.4oC; 92% at 42.7oC, 46% at 43oC). Hypothermia (Tc < 34.5oC) developed following heat stress with the depth and duration of hypothermia significantly enhanced in the moderate and extreme compared to the mild group. Regardless of heat stress severity, every mouse that transitioned out of hypothermia (survivors only) developed a virtually identical elevation in Tc the following day, but not night, compared to non-heated controls. To test the effect of recovery Ta, a group of mice (N-5) were acclimated for > 4 weeks and recovered at Ta of 3OoC following moderate heat stress. Recovery at 30oC resulted in 0% survival within ^2hh following cessation of heat stress. Using biotelemetry to monitor Tc in the unrestrained mouse, we have shown that recovery from acute heat stress is associated with prolonged hypothermia followed by an elevation in daytime Tc that is dependent on Ta. These thermoregulatory responses to heat stress are key biomarkers that may provide insight into heat stroke pathophysiology.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2005
- Accession Number
- ADA430342
Entities
People
- Clifford W. Mason
- David A. Dubose
- Lisa R. Leon
Organizations
- United States Army Research Institute of Environmental Medicine