The purpose of this study is to explore possible potential implications of cold air in cardiovascular disease (CVD) risk in rats. Healthy Wistar rats were exposed to artificial cold air under laboratory conditions, and their systolic blood pressure, heart rate, vasoconstriction, CVD risk factors, and myocardial damage indicators after cold air exposure were determined and evaluated. Systolic blood pressure, whole blood viscosity, and plasma level of norepinephrine, angiotensinⅡ, low density lipoprotein, total cholesterol, and fibrinogen in treatment groups increased significantly compared with control groups. No significant variations were found in plasma Mb and cTnT and myocardial tissue between the treatment and control groups. Results indicate that: (1) higher levels of SBP, WBV and LDL/HDL, total cholesterol (TC), and FG in blood may indicate higher CVD risks during cold air exposure; (2) cold air may exert continuous impacts on SBP and other CVD risk factors.

The purpose was to investigate the effects of artificial cold air on cardiovascular risk in hypertensive subjects. An artificial cold air was simulated with hourly ambient temperature data of a real moderate cold air in China. Twenty-four male SHR rats were randomly divided into the minimum temperature (Tmin) group, the rewarming temperature (Tr) group and two concurrent control groups with six rats in each (Tmin and Tr represent two cold air time points, respectively). Tmin and Tr groups were exposed to the cold air that was stopped at Tmin and Tr, respectively. After cold air exposure, blood pressure, heart rate and body weight were monitored, blood was collected for the detection of some indexes like fibrinogen, total cholesterol and uric acid. Results demonstrated that blood pressure, whole blood viscosity, blood fibrinogen, total cholesterol and uric acid increased significantly both in the Tmin and Tr groups; low density lipoprotein/high density lipoprotein increased significantly only in Tr group; there was higher level of blood fibrinogen in the Tr group than the Tmin group; higher levels of creatine kinase-MB was found in both the Tmin and Tr groups. These results suggest that cold air may increase the cardiovascular risks in hypertensive subjects indirectly through its effects on the sympathetic nervous system and renin angiotensin system, blood pressure and atherosclerosis risk factors like blood viscosity and fibrinogen, lipids and uric acid in the blood.

Ten-week-old male Wistar rats (systolic blood pressure, 106-116 mmHg; body weight, 300-320 g) and spontaneously hypertensive rats (systolic blood pressure, 160-176 mmHg; body weight, 210.9-244.9 g) were used as healthy and hypertensive subjects to determine the effects of varying degrees of cold-air exposure in a climate chamber box. The three cold-air ranks were cold air I [minimum temperature (TMIN) 6.4 °C, ↓∆T48 8.6 °C], cold air II (TMIN 3.8 °C, ↓∆T48 11.2 °C), and cold air III (TMIN -0.3 °C, ↓∆T48 15.3 °C), as established from the cold-air data of Zhangye City, China. Each cold-air rank consisted of a temperature drop and a temperature increase with the same initial and terminal temperatures (15 °C). After cold-air exposure, the risk factors for cardiovascular disease (CVD) such as systolic blood pressure, whole blood viscosity (10/s and 150/s), plasma fibrinogen, and blood lipids of the rats were determined. The results indicated that the CVD risk factors of the healthy and hypertensive rats increased significantly with cold-air exposure intensities. The increase in systolic blood pressure was greater during temperature drops, whereas the increases in whole blood viscosity and plasma fibrinogen were greater after cold-air exposure. The effects of cold-air exposure on the CVD risk factors of healthy rats, particularly the systolic blood pressure, whole blood viscosity (150/s), and LDL/HDL, were greater than those in hypertensive rats. In conclusion, CVD risk may increase with cold-air ranks. Blood pressure-induced CVD risk may be greater during cold-air temperature drop, whereas atherosclerosis-induced CVD risk may be greater after cold-air exposure. The effect of cold air on the CVD risk factors in healthy subjects may be more significant than those in hypertensive subjects.

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