Aim To explore the effects of Angiotensin II on the activities of Ca²⁺-ATPase, Na⁺, K⁺-ATPase and mRNA expression levels of the plasma membrane Ca²⁺-ATPase isoform 1 (PMCA1) and Na⁺, K⁺-ATPase α₁-subunit in cultured thoracic aortic vascular smooth muscle cells (AMSCs) from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR).

Methods AMSCs isolated from 14-week-old male WKY rats and SHR were cultured and treated with different concentrations (1×10⁻⁹, 1×10⁻⁸, 1×10⁻⁷ mol/l) of Angiotensin II. The activities of Ca²⁺-ATPase, Na⁺, K⁺-ATPase were measured by biochemistry and enzymology. RT-PCR assay was employed to determine the relative levels of PMCA1 and Na⁺, K⁺-ATPase α₁-subunit mRNA in AMSCs.

Results Low and moderate concentration of Angiotensin II significantly increased the activity of Ca²⁺-ATPase and up-regulated PMCA1 mRNA level in AMSCs from Wistar-Kyoto rats, while high concentration of Angiotensin II inhibited Ca²⁺-ATPase activity and down-regulated PMCA1 mRNA level. Three different concentration of Angiotensin II significantly decreased the activity of Ca²⁺-ATPase and PMCA1 mRNA level in AMSCs from SHR. Three different concentrations of Angiotensin II stimulated the activity of Na⁺, K⁺-ATPase and increased its α₁-subunit mRNA expression in AMSCs from WKY rats. Low and moderate concentration of Angiotensin II did not affect the activity of Na⁺, K⁺-ATPase in SHR, while high concentration of Angiotensin II significantly suppressed the activity and α₁-subunit mRNA level of Na⁺, K⁺-ATPase.

Conclusions In WKY rats, Angiotensin II may have biphasic effects on Ca²⁺-ATPase activity and PMCA1 mRNA expression, and may promote the activity and α₁ subunit mRNA expression of Na⁺, K⁺-ATPase in a dose-dependent manner in AMSCs. In SHR, Angiotensin II can inhibit Ca²⁺-ATPase activity and PMCA1 mRNA expression, and only high dose of Angiotensin II can suppress the activity and α₁ subunit mRNA expression of Na⁺, K⁺-ATPase in AMSCs.