Journal of Applied Physiology, Vol 68, Issue 4 1337-1342, Copyright © 1990 by American Physiological Society

ARTICLES

Thermal adjustments to nonexertional heat stress in mature and senescent Fischer 344 rats

K. C. Kregel, C. M. Tipton and D. R. Seals
Department of Exercise and Sport Sciences, University of Arizona, Tucson 85721.

The purpose of this study was to test the hypothesis that the rise in colonic temperature (Tc) during nonexertional heat stress is exaggerated in senescent (SEN, 24 mo, n = 12) vs. mature (MAT, 12 mo, n = 15) conscious unrestrained Fischer 344 rats. On 2 separate days (48 h apart) each SEN and MAT animal was exposed to an ambient temperature (Ta) of 42 degrees C (relative humidity 20%) until a Tc of 41 degrees C was attained and then cooled at a Ta of 26 degrees C until Tc returned to the initial control level. Control Tc was similar in the two groups for both trials. The rate of Tc change during heating was 63% greater (0.070 +/- 0.005 vs. 0.043 +/- 0.004 degrees C/min, P less than 0.05) and the time to 41 degrees C reduced by 36% (54 +/- 6 vs. 85 +/- 10 min, P less than 0.05) in MAT vs. SEN animals during the first exposure, although the cooling rate was slower in the MAT (0.048 +/- 0.004 degrees C/min) vs. SEN (0.062 +/- 0.006 degrees C/min) animals (P less than 0.05). The heating rate was unchanged in MAT animals between trials 1 and 2. However, SEN animals had a 95% increase in heating rate in trial 2 compared with trial 1 (P less than 0.05), and the corresponding time to 41 degrees C was decreased by 44% (P less than 0.05). As a result, rate of heating and time to 41 degrees C were similar in the two groups during trial 2. The cooling rate was similar between trials within each group.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				T. D. Oberley, J. M. Swanlund, H. J. Zhang, and K. C. Kregel Aging Results in Increased Autophagy of Mitochondria and Protein Nitration in Rat Hepatocytes Following Heat Stress J. Histochem. Cytochem., June 1, 2008; 56(6): 615 - 627. [Abstract] [Full Text] [PDF]

				H. J. Zhang, S. R. Doctrow, L. W. Oberley, and K. C. Kregel Chronic antioxidant enzyme mimetic treatment differentially modulates hyperthermia-induced liver HSP70 expression with aging J Appl Physiol, April 1, 2006; 100(4): 1385 - 1391. [Abstract] [Full Text] [PDF]

				D. M. Hall, L. Xu, V. J. Drake, L. W. Oberley, T. D. Oberley, P. L. Moseley, and K. C. Kregel Aging reduces adaptive capacity and stress protein expression in the liver after heat stress J Appl Physiol, August 1, 2000; 89(2): 749 - 759. [Abstract] [Full Text] [PDF]

				D. M. HALL, T. D. OBERLEY, P. M. MOSELEY, G. R. BUETTNER, L. W. OBERLEY, R. WEINDRUCH, and K. C. KREGEL Caloric restriction improves thermotolerance and reduces hyperthermia-induced cellular damage in old rats FASEB J, January 1, 2000; 14(1): 78 - 86. [Abstract] [Full Text]

				M. P. Massett, S. J. Lewis, J. N. Bates, and K. C. Kregel Modulation of temperature-induced tone by vasoconstrictor agents J Appl Physiol, March 1, 1999; 86(3): 963 - 969. [Abstract] [Full Text] [PDF]

				H. J. Zhang, V. J. Drake, J. P. Morrison, L. W. Oberley, and K. C. Kregel Molecular Biology of Thermoregulation: Selected Contribution: Differential expression of stress-related genes with aging and hyperthermia J Appl Physiol, April 1, 2002; 92(4): 1762 - 1769. [Abstract] [Full Text] [PDF]