Intensified catabolism with activated proteolysis caused by stress and high temperature as a physical and chemical factor was found to be the typical response of the human body at the first stage of acute overheating. The data on the glutathione, which detoxifies lipid peroxides and protects proteins from oxidation, showed that hyperthermia strained the body antioxidant mechanisms. The body resistance to overheating depended on its initial status characterized by specific metabolic conditions.
Key Words: humans; overheating; glutathione system; proteolysisThe research interest in the problem of overheating has not decreased in recent decades [2,6,7,15]. The biochemical and molecular mechanisms underlying the compensatory and adaptive reactions to overheating are not well understood. These regulatory mechanisms seem to determine the variability of the human body resistance to external overheating. Our objective was to study general characteristics of physiological and metabolic processes occurring in human body exposed to acute overheating and to analyze individual characteristics which determine the body resistance to hyperthermia.
MATERIALS AND METHODSThe study involved 49 healthy volunteers in the age range of 20-25 years. After their functional conditions and working capacities had been assessed at comfort temperature, they were exposed to heat in a Tabaj climatic complex (45~ air temperature at a 45% humidity and a 1-2 m/sec air flow rate). During the test the subjects were dressed in isolating water-proof clothes and performed veloergometric exercise with a controlled workout to accelerate hyperthermia. RectalMilitary Medical Academy, St-Petersburg, Russia temperature and cardiovascular indices were recorded during the test. Rectal temperature of 39.5~ or the subject's discomfort with the refusal to continue the test were taken as the threshold endurance. Samples of venous blood and urine were taken Ior biochemical analysis 1 h prior to the exposure and 10-20 min after it.The index of thermosensitivity (ITS) was calculated to assess the level of strain in a thermoregulatory system. It was determined as the index of thermal strain divided by the time of exposure. The index of thermal strain (IS) was calculated from the following formula [9]: IS=2.5 xd T+0.125 xdW+0.012xdPs, where dT is the increase in rectal temperature, "C, dW is the rate of water loss, g/min, and dPs is the increase in heart rate (HR), beats/min.The subjects were divided into three groups in accordance with low, medium, and high indices of ITS that reflect the level of strain in their thermoregulatory systems.The concentration of TBA-reactive products in blood plasma was determined in the samples taken with heparin [1]. The total content of low-and medium-molecular-weight compounds and oligopeptides 0007-4888/99/0001-0014 $22.00 9
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