Study on the Antihypertensive Effect of Extract at Different Temperatures of Dendrobium Officinale on Spontaneous Hypertension Rats

OBJECTIVE To observe the antihypertensive effect and its possible mechanism of extraction of Dendrobium officinale extracted at different temperatures on spontaneous hypertension rats(SHR). METHODS Half male and half female, totally 48 SHR rats were randomly divided into Dendrobium officinale 60℃ water extraction group(0.8 g·kg^-1·d^-1), 100℃ water extraction group(0.8 g·kg^-1·d^-1), 121℃ water extraction group(0.8 g·kg^-1·d^-1), 60℃-100℃-121℃ gradient temperature water extraction group(0.8 g·kg^-1·d^-1), positive drug group(0.5 mg·kg^-1·d^-1 amlodipine besylate tablets) and model group, and eight Wistar rats were set as normal group. The blood pressure was measured at 2, 24 h after administration once a week. After 8 weeks of treatment, plasma renin activity(PRA), and the contents of aldosterone(ALD), angiotensin I(Ang I) and angiotensin II(Ang II) in plasma were detected by chemiluminescence; the mRNA expression of angiotensin converting enzyme(ACE) in pulmonary tissue, angiotensinogen(AGT) in liver tissue, aldosterone synthetase(CYP11B2) in renal tissue, Ang Ⅱ type 1 receptor(AT1R), endothelin-1(ET-1) were detected by RT-qPCR. RESULTS After 8 weeks of treatment, the systolic pressure and diastolic pressure at 2 h after administration in each treatment groups were significantly lower than that in the model group(P<0.01), among them, the pressure relief of Dendrobium officinale in different temperature water extraction group was similar to that of the positive drug group, there was little difference in antihypertensive effect among groups; after 7-8 weeks of treatment and at the third day after withdrawal, the systolic blood pressure after 24 h in each treatment groups were significantly lower than that in the model group(P<0.05 or P<0.01); after 7 weeks of treatment and at the third day after withdrawal, the diastolic pressure after 24 h in each treatment groups were significantly lower than that in the model group(P<0.05 or P<0.01); the pressure relief at 24 h in Dendrobium officinale different temperature extraction group was similar to that of the positive drug group, and there was no significant difference in blood pressure reduction between groups in 8 weeks of treatment. There were no significant differences between the normal group, model group and each treatment groups of the levels of Ang I, Ang II, PRA and ALD in plasma; the expression of the AT1R mRNA in the model group were significantly higher than the normal group, the expression of the AT1R mRNA in the 100℃ water extraction group, 121℃ water extraction group and positive drug group were significantly lower than in the model group(P<0.05). CONCLUSION Extractions of Dendrobium officinale at different temperature can significantly reduce the blood pressure in SHR rats, while there is a difference in the polysaccharide content. And the antihypertensive effect may be related to the down-regulating AT1R, the effect of water extraction under different temperatures is similar, and the hypotensive effect is close to that of western medicine antihypertensive drug(amlodipine besylate tablets). The antihypertensive effect of Dendrobium officinale and polysaccharide content may not be directly related.