Effects on rats of exposure to heat and vibration

¹ Bioastronautics Section, Aero-Space Division, The Boeing Company, Seattle, Washington

Restrained adult male rats of the Sprague-Dawley strain were exposed for a 20-min duration to sublethal intensities of heat, vibration, and to the combination of heat and vibration. The incidence of mortality resulting from simultaneous exposure to both environmental stresses was significantly greater than would be predicted if these stresses were to act independently of each other. Hematocrit, hemoglobin, and serum glutamic-oxalacetic transaminase levels were significantly elevated immediately after vibration. Heat in combination with vibration increased these values although heat stress per se caused no change from control levels. Twenty-four hours after exposure to the combination of vibration and heat, hematocrit and hemoglobin levels returned to normal but the serum glutamic-oxalacetic transaminase levels were still significantly elevated. Significant increases in heart, kidney, and adrenal weights were observed immediately after exposure to the combination of environmental stresses. Possible modes of action are discussed.