Vasoconstrictive effect of <i>Xinmailong</i> injection in rat aorta

Abstract

Background: Cockroach has been traditionally utilized in China for the therapy of cardiovascular  disorders, such as heart failure. The present study was aimed to assess the vasoconstrictive effect of  Xinmailong Injection (XML), a bioactive composite from American cockroach.
Methodology: The isometric tensions of rat aortic rings were measured after acutely treated with XML. Meanwhile, the systemic blood pressures (SBPs) were recorded and the levels of the endothelium-derived cytokines in blood samples were detected after rats were administered with XML for 3 days. Protein expression for the L-type Ca²⁺ channels (Ca_v1.2) was also determined in rat thoracic aorta.
Results: XML induced vasoconstrictions in rat aortic rings with or without endothelium. In addition, the vasoconstrictions due to the extracellular Ca²⁺ influx and the intracellular Ca²⁺ release were also  elevated by XML. After treatment with XML for 3 days, the level of prostacyclin (PGI2) was markedly increased whereas the levels of nitric oxide (NO) and endothelin-1 (ET-1) were not significantly changed in rats. Furthermore, expression of the Ca_v1.2 protein was significantly enhanced in aorta but the SBPs of  rats were not influenced.
Conclusion: XML plays an important role in regulating vascular tone. The increases of the extracellular  Ca²⁺ influx and the intracellular Ca²⁺ release may contribute to the vasoconstriction induced by XML. Our findings pave the ways to the better understandings of the therapeutic effects of XML on cardiovascular system.

Key words: Xinmailong Injection; American cockroach; Vasoconstriction.