Hemodynamic responses to severe heat stress in rats: implications for blood pressure regulation (1104.20)
Abstract
Increases in heart rate (HR) and cardiac output, and redistribution of blood flow to the periphery are key cardiovascular responses to heat exposure. We previously observed hysteresis in the HR response to heating in rats, whereby HR was higher for a given core temperature (Tc) during cooling/recovery compared to during heating. In the present study, we evaluated whether this hysteresis was associated with dehydration, and whether specific cardiovascular response patterns were associated with more negative outcomes. Tc, HR and arterial pressure were measured via radiotelemetry in conscious male Fischer 344 rats (n=22; 272.4 ± 4.7 g) during exposure to 37°C (heating phase) and during recovery at 20°C (cooling phase). HR increased substantially during heating. At Tc = 39.5°C, HR was 386 ± 5 bpm during the heating phase and 490 ± 14 bpm during the cooling phase (P< 0.001). HR hysteresis in recovery was coincident with substantial dehydration (7‐8%BW), but returned to baseline after ~20 min despite continued dehydration, suggesting these events were not linked. Independent of hysteresis, rats with the worst outcomes demonstrated a drop‐off in HR at end of heating. These findings provide further insight into multiple simultaneous stressors placed on integrative cardiovascular regulation during and immediately following heat stress.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2014
- Source ID
- 10.1096/fasebj.28.1_supplement.1104.20
Entities
People
- Carrie Quinn
- Lisa Leon
- Nisha Charkoudian
- Rocio Duran
Organizations
- United States Army Medical Research and Development Command
- United States Army Research Institute of Environmental Medicine