Acute Heat/Exercise Stress in Rats: Effects on Fluid and Electrolyte Regulatory Hormones,
Abstract
Adult, male rats were exercised (level treadmill, 9.14 m/min) in the heat (35 C, 30-35% rh) until hyperthermic exhaustion (T sub re = 42.5 - 43 C) ensued. Blood samples (0.3 ml) were taken immediately prior to exercise in the heat (time 0), when T sub re reached 40 C (8.25 min treadmill time), when hyperthermic exhaustion occurred, and again when T sub re decreased to 40 C. Plasma was separated and assayed for aldosterone, angiotensin I (plasma renin activity), and antidiuretic hormone (arginine-vasopressin). Plasma aldosterone levels were significantly (p<.001) elevated after 8 min of exercise and remained increased throughout the exercise and recovery periods. Alternatively, plasma angiotensin I levels were unaffected during exercise, but increased significantly (p<.001) during the recovery period. Arginine-vasopressin concentrations were likewise significantly (p<.05) elevated by completion of the exhaustive run and continued to increase during the recovery period. We attributed these elevations in levels of the fluid and electrolyte regulatory hormones to part of an adaptational response to maintain or increase plasma volume during exercise in the heat. Significant (p<.001) decrements in hematocrit ratio occurred during the exercise interval. However, we were unable to relate the ultimate ability of the animal to survive the heat/exercise-induced injury to the intensity of its hormonal response pattern to exercise in the heat.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 20, 1982
- Accession Number
- ADA110559
Entities
People
- Milton Mager
- Ralph Francesconi
Organizations
- United States Army Research Institute of Environmental Medicine