[5-Hydroxyindoleacetic acid and creatinine excretion in thermal stress]

The determination of 5-HIIA and creatinine excretion in thermal stress was performed in two series, in the first (I) on 102 healthy men aged 20--45 yrs (58 smokers and 55 non-smokers) and in the second one (II) on 20 men after drinking of 1 1 water immediately before thermal stress. The subjects remained at rest in the climatic chamber for 90 min in the temperature of 45 +/- 1 degrees C and relative humidity of 70 +/- 5 per cent. Thermal stress resulted in a significant increment of body temperature after 45 min and after consecutive 45 min of exposure, and lack of steady state. Creatinine and 5-HIIA were determined in two urine portions after 45 and after consecutive 45 min of exposure. Total amounts of excreted 5-HIIA and creatinine in the first urine portion in (I) and (II) were significantly higher in comparison with normal values; they did not depend on the amount of urine voided. The 5-HIIA excretion was significantly higher in smokers after the first 45 min of exposure only. Total amounts of excreted 5-HIIA and creatinine after another 45 min of exposure in (I) and (II) were significantly lower. The high correlation has been found between excretion of 5-HIIA and creatinine, indicating a similar process of excretion of both substances. Hydratation before the thermal stress exerted advantageous effect on the thermoregulation in men. The results of this study have been discussed in conjunction with the data in literature.