Effects of total flavonoids of Hippophae 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 of Hippophae rhamnoides L. (TFH), quercetin (Que) and isorhamnetin (Isor) on the intracellular free calcium ([Ca(2+)](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 (100 mg/L) and its essential monomers, namely Que (10(-4) mol/L) and Isor (10(-4) mol/L) on changes of [Ca(2+)](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 [Ca(2+)](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 Ca(2+), 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 Isor might decrease the levels of [Ca(2+)](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.