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.