Effects of Total Flavonoids ofHippophae Rhamnoides L. on intracellular free calcium in cultured vascular smooth muscle cells of spontaneously hypertensive rats and Wistar-Kyoto rats

Objective: To explore the effects of total flavonoids ofHippophae rhamnoides L. (TFH), quercetin (Que) and isorhamnetin (Isor) on the intracellular free calcium (Ca²⁺ ]_i) in vascular smooth muscle cells (VSMC) of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY).Methods: Fluo 3-acetoxymethylester(Fluo-3/AM) was used to observe the effects of TFH (100mg/L) and its essential monomers, namely Que (l0^-4 mol/L) and Isor (l0^-4 mol/L) on changes of Ca²⁺]_i in cultured SHR and WKY VSMC (abbr. to Ca-SHR & Ca-WKY) following exposure to high K⁺, norepinephrine (NE) and angiotensin II (Ang II), and to compare with the effects of verapamil (Ver).Results: (1) TFH, Que and Isor had inhibitory effects on resting Ca-SHR (P<0.05), but had no significant effects on Ca-WKY (P>0.05). (2) High K⁺ could increase Ca-SHR more significantly than Ca-WKY (P<0.05); TFH, Que and Isor could inhibit the elevation of Ca²⁺]_i induced by high K⁺-depolarization, with the effects similar to that of Ver, and the effect on Ca-SHR was more significant than that on Ca-WKY (P<0.05). (3) NE and Ang II could increase Ca-SHR more significantly than Ca-WKY (P<0.05), TFH, Que and Isor had remarkably inhibitory effect on the elevation of Ca-SHR and Ca-WKY induced by NE or Ang II. (4) In the absence of extracellular Ca²⁺, TFH, Que and Isor also had certain inhibitory effect on Ca-SHR and Ca-WKY induced by NE, and the effect on the former was more significant than that on the latter(P<0. 05).Conclusion: TFH, Que and lsor might decrease the levels of Ca²⁺]_i in VSMCs by blocking both voltage-dependent calcium channels (VDC) and receptor-operated calcium channels (ROC) in physiological or pathological state, which may be one of the important mechanisms of their hypotensive and protective effects on target organs in patients with hypertension. Supported by One-hundred-people Plan of Hygiene System in Shanghai (No. 990122)