Effect of dehydration heat exposure on thoracic aorta reactivity in rats.

The aim of the present study was to investigate the effect of one week dehydration heat exposure on thoracic aorta reactivity in rats. Eighteen Male Sprague-Dawley rats were randomly divided into 3 groups (n=6 each group): Control group (CN), heat exposure group (HE), dehydration heat exposure group (DHE). The CN group was exposed to a room temperature of 24°C, while the HE and DHE groups were exposed to a heat temperature of 32°C. After 7 days of heat exposure, the heart rate and blood pressure of the rats were measured, and the noradrenaline (NA)-induced contraction on the aorta rings was measured by tension recording. The average contents of malondialdehyde (MDA) and superoxide dismutase (SOD) in serum were detected using ELISA. The expression of apoptotic genes in the thoracic aorta was measured using RT-PCR. Compared with CN, the heart rate in the HE and DHE groups had a tendency to become retarded, but there was no significant difference (P>0.05). In the HE group, the systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) of the rats were significantly higher than that of the CN (P<0.05). In the DHE group, the SBP of rats was significantly higher than that of the CN (P<0.05), while the SBP, DBP, and MAP of the rats were decreased compared to the rats in the HE group, although there was no statistical significance (P>0.05). In the HE and DHE groups, the NA-induced contraction on the rats thoracic aorta ring was larger than that of the CN (P<0.05), albeit there was no significant difference between the HE and DHE groups (P>0.05). The serum SOD content decreased in the HE and DHE groups, however, the reduction was significant only in the DHE group (P<0.05). The content of MDA in serum was significantly increased in the DHE group (P<0.05). The expression of BAX was significantly upregulated whereas Bcl2 expression was decreased in the DHE group (P<0.05). The results showed that a high temperature was harmful to the body, especially in the case of lack of food and water. Additionally, the heat exposure elevated blood pressure, and increased arterial reactivity, which were related to the elevated production of MDA, led to the impaired production of SOD, and an increase of cell apoptosis. These findings are useful to understand the influence of dehydrated heat exposure on the vascular function, and they provide certain theoretical and experimental guidance for protection under high temperature.