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Use of Biomarkers to Optimize Heat Acclimation in Women

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Annual rept. 25 Sep 95-24 Sep 96

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These experiments determined if estrogen E2 supplementation in a menstruating young women during the follicular phase of their menstrual cycle, or b ovariectomized female rats would promote heat loss in women and enhance thermotolerance in animals. Women 11 CONTROL P, 10 experimental e performed cycle exercise at 60 VO2 max in a cool 25 deg C room for 20 min. Neither sweating threshold 36.97 or -0.15 deg C in P vs 36.9 or -0.22 deg C in E, threshold to increase forearm blood flow 37.09 or -0.22 deg C in P vs 37.17 or -0.26 deg C in E, slope of the sweatingesophogeal temperature relationship 0.42 or -0.16 in P vs 0.41 or -0.17 in E, or the slope of the forearm blood flowesophogeal temperature relationship 10.04 or -4.4 in P vs 9.61 or -3.46 in E were affected by 3 days of E2 supplementation. In the animal study, rats received daily subcutaneous injections of either a vehicle sesame oil n18 or estradiol 10 ug100ml g b.w. n18. Within each group, 3 subgroups were utilized a 4-day, b 8-day, or c 12-day treatment. Four hours after the final daily injection, rats underwent a heat tolerance test HTT consisting of treadmill exercise at 21.5 mmin at 35 deg C until colonic temperature Tc reached 40.4 deg C. Vehicle treatment had no effect on initial Tc, time to reach 40.4 deg C, or heating rate between treatments. However, initial Tc values were reduced, heating rates were lower, and times to reach 40.4 deg C were increased in rats treated with E2 for 8 and 12 days compared with the 4-day treated group P0.05. Moreover, both initial Tc and heating rate were lower and time to 40.4 deg C was higher in E2- vs vehicle-treated rats for both 8- and 12-day protocols.

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  • Medicine and Medical Research
  • Stress Physiology

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