, 15:1 | Cite as

Effects of aging on cutaneous regional and superficial capillary blood flows during heat stress in the rat

  • Kathleen A. Westphal
  • Daniel R. Richardson


The purpose of this study was to investigate the effects of aging on the cutaneous circulatory response to heat stress. Young (6–8 too) and old (22–24 mo) Fischer 344 rats were placed unanesthetized in an environmental chamber arranged so that the body could be heated while the tail remained at ambient temperature (23°C Total blood flow (TBF) to the tail was measured via strain gauge plethysmography while the cutaneous microcirculation was investigated by way of videomicroscopic measurements of capillary blood cell velocity (CBV) and the density of flow active capillaries (DFC) within the subepidermal vascular plexus of the tail. The measurements of CBV were multiplied by vessel cross sectional area and DFC to obtain a calculated variable termed the capillary perfusion index (CPI). As chamber temperature was increased in a stepwise manner from 23° to 40°C TBF and CPI significantly increased in both young and old animals (P≤0.001) with the rise in CPI being mediated by changes in both CBV and DFC. Colonic temperature (Tc) tended to be lower in the old group up to a chamber temperature of 40°C at which point the old animals had a higher Tc. At the initial chamber temperature of 23°C the CPI/TBF ratio was significantly higher in the old compared to the young rats (P≤0.05), and as chamber temperature increased this ratio decreased in the old (P≤0.030) but not in the young animals. This finding suggests that heat stress in an older organism requires a greater total cutaneous blood flow response in order to maintain sufficient flow in the subepidermal plexus for heat liberation.


Heat Stress Chamber Temperature Circulatory Response Vascular Plexus Heat Liberation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© American Aging Association, Inc. 1992

Authors and Affiliations

  • Kathleen A. Westphal
    • 1
  • Daniel R. Richardson
    • 1
  1. 1.Department of Physiology and Biophysics, Sanders-Brown Research Center on AgingUniversity of Kentucky Medical CenterLexington

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