Cold temperature can cause serious damage to the body, and it is imperative to find a reasonable means to improve the body’s cold resistance. Cold temperature can lead to increased free radicals in the body, the cyclic nucleotides have a certain relationship with cold adaptation. Vitamin E is an important free radical scavenger in the body, which has a significant effect on improving the cold tolerance of animals exposed to cold temperature. Sea buckthorn oil extracted from sea buckthorn fruits is rich in vitamin E and carotene and has anti-lipid peroxidation. The purpose of this study was to investigate the mechanism of anti-cold effects of sea buckthorn oil.

1 Method
After sea buckthorn oil was fed to cold-exposed rats, the following indicators were determined and observed:
(1) cyclic adenosine monophosphate (cAMP), cyclic-guanosine monophosphate (cGMP)
(2) serum lipid peroxide (LPO)
(3) Whole blood GSH-Px activity
(4) Whole blood SOD activity
The results were compared with control rats at room temperature.

2 Results
2.1 Effects of sea buckthorn oil on plasma cyclic adenosine monophosphate content in rats exposed to cold temperature.
(1) Plasma cAMP levels in the cold-exposed control group were significantly higher than the room temperature control group (P<0.01) after 1 week and 2 weeks;
(2) The plasma cGMP levels in the cold-exposed control group were significantly higher than those in the room-temperature control group after 1 week and 2 weeks.
2.2 The content of LPO in the blood of rats exposed to cold temperature fed with sea buckthorn oil.
The effect of GSH-Px and SOD activity:
serum LPO content in cold exposed control group was significantly higher than that in room temperature control group (P<0.01).

After 1 week of cold exposure, the activities of GSH-Px and SOD in blood were significantly higher than those in room temperature control group (P<0.01). After 2 weeks, the activities of the two enzymes were significantly lower than those in room temperature control group (P<0.01).

3 Discussion
Cold temperature damage is extremely harmful to the body. How to resist cold temperature is an important issue that people are very concerned about. It is particularly important to improve the cold resistance of the body for troops in cold regions and workers under low temperature conditions. Sea buckthorn oil contains not only a large amount of vitamin E, but also contains a certain amount of carotene, which has anti-lipid peroxidation effect. Cold temperature damage is closely related to free radical damage caused by tissue cells and cyclic nucleotide metabolism in the body.

3.1 Effects on lipid peroxidation
The results of this experiment indicate that the LPO content in the blood of rats exposed to cold temperature was significantly increased, but there was no significant increase after sea buckthorn oil supplementation, which was close to the room temperature control group. It indicated that sea buckthorn oil had obvious inhibitory effect on lipid peroxidation in cold-exposed rats, thus protecting the body from damage caused by cold temperature.

3.2 Effects on GSH-Px and SOD activity
GSH-Px and SOD are important antioxidants. The results of this study indicate: after rats were exposed to cold temperature for 1 week. The activity of the two enzymes in the blood increased significantly but decreased significantly after 2 weeks. This may be because the organism is experiencing an increase in local free radicals. It can stimulate and activate the antioxidant enzyme activity of local tissues to some extent, especially SOD activity, trying to achieve a new balance between oxidation and anti-oxidation to improve the local antioxidant capacity. However, the compensatory mechanism of the body is not complete.

The increase of antioxidant enzyme activity after cold exposure did not eliminate the oxidative damage of tissue cells by increased oxygen free radicals. After 2 weeks, the LPO content continued to be significantly higher than that of the room temperature group. The body will consume a large amount of GSH-Px and SOD to remove LPO, so its activity is reduced. Sea buckthorn oil contains vitamin E and carotene, which are important antioxidants, which have certain protection and supplement effects on these two enzymes. The change in enzyme activity was not significant and was close to the room temperature control group.

3.3 Effects on cAMP and cGMP content:
Cold exposure was observed in the study to increase cAMP and cGMP in animals. The change in the experimental group was not obvious, because sea buckthorn oil had anti-lipid peroxidation as a nutrient. Therefore, the tissue cells can be protected from the cold, and the body can be adapted to the cold and improve the cold resistance of the body. However, the supplementation of sea buckthorn oil has no significant effect on cGMP content. The mechanism needs to be further explored.
It is believed that sea buckthorn oil can affect the body’s cold adaptation by affecting the body’s cyclic nucleotide metabolism and its anti-lipid peroxidation and improve the body’s cold tolerance. It is a natural anti-cold resource.