The effect of high ambient temperature on acid-base balance and electrolyte parameters in rats

Abstract

Exposure to high environmental temperature could lead to different heat-related illness as well as worsening some disease conditions. Thirty rats were used to determine the nature of the disturbances of the acid-base balance and electrolytes of blood serum after exposure to high ambient temperature. Twenty rats which formed the experimental group were exposed to sun for 30 minutes daily for two weeks, while the remaining rats served as the unexposed control group. The serum pH, serum HCO₃^- and electrolytes of both the groups in the first week and the second week were obtained using pH meter, back titration, flame photometry, mercurite titrimetric and spectro-photometry. Histopathology of the lungs and kidneys of rats from each group was carried out using basic histological technique. Results show decreased level of serum HCO₃^- and increased level of serum pH in the experimental group. In the second week there is significant difference in HCO₃^- levels (p<0.05). The serum pH in 1^st and 2^nd week did not show any significant difference in regard to change in the temperature. The findings also showed that high ambient temperature have significant effect on serum sodium (Na⁺), serum chloride (Cl^-) and serum potassium levels (K) (p<0.05); but did not affect serum calcium (Ca⁺) level (p>0.05). There is glomerular degeneration, interstitial haemorrhage and tubular distension due to fluid retention in the kidney as revealed by the photomicrograph of the exposed rat kidneys. In the lungs of the exposed rat, there is mild interstitial haemorrhage and peribronchoilar epithelial shading. In conclusion, this study indicates that serum calcium is not significantly affected like in the case of serum sodium, chloride and potassium during heat stress and respiratory alkalosis is the predominant acid-base disorder in rats exposed to sun due the occurrence of hyperventilation in heat stress. This research provided some references of acid-base and electrolytes disorder in rats exposed to high ambient temperature.