Objectives To observe the effect of high temperature, noisy, and combined environment on blood pressure, heart rates, vasoactive substances in rats.

Methods Rats were divided randomly into 6 groups with 10 rats in each group. They were normal control group, high temperature group, low-frequency noise group, high-frequency noise group, high-temperature low-frequency noise group, and high-temperature high-frequency noise group. Rats were exposed continuously for 3 hours each day to appropriate environment for 30 days. Blood pressure, heart rate were measured, and plasma adrenaline, endothelin-1 and nitric oxide content were determined.

Results No significant difference was observed on heart rate of exposed groups with the normal control group, excepting the heart rate of rats in high temperature groups was clearly lower than the rest of exposed groups (P less than 0.05). No significant difference was observed on blood pressure of high temperature group and high-temperature low-frequency noise group compared with normal control group. Blood pressure in low-frequency noise group and high-frequency noise group was significantly higher than that in the normal control group (P less than 0.05, 0.01). Blood pressure in high-temperature high-frequency noise group was significantly lower than that in normal control groups (P less than 0.05, 0.01). No significant difference was observed on plasma adrenaline content of high temperature group, low-frequency noise group and high-frequency noise group compared with the normal control group.Plasma adrenaline content of high-temperature low-frequency noise group was significantly higher than that of the normal control group, high temperature group, low-frequency noise group and high-frequency noise group (P less than 0.05, 0.01).Plasma adrenaline content of high-temperature high-frequency noise group was significantly higher than that of the normal control group and the rest of exposed groups (P less than 0.05, 0.01). No significant difference was observed on plasma nitric oxide content of high temperature group, and high-frequency noise group compared with the normal control group. Plasma nitric oxide content of low-frequency noise group was significantly higher than the normal control group (P less than 0.01). Plasma nitric oxide content of high-temperature low-frequency noise group was significantly higher than that of the normal control group and high temperature group (P less than 0.01). No significant difference on plasma nitric oxide content of high-temperature high-frequency noise group compared with the normal control group, high temperature group and high-frequency noise group.

Conclusions High temperature and noisy could increase the release of endothelin-1 from vascular endothelial cells. Noisy environment could cause the rise of systolic blood pressure and diastolic blood pressure and release more endothelin-1 and release less nitric oxide from vascular endothelial cells. The stimulation of high temperatures and noise combined environment could cause a resistance of cardiovascular system to adrenaline and endothelin-1.