Contractile Effect Of Polysaccharide Sulfate On Rat Thoracic Aortas In Vitro

AIM The objective of the present study was to examine the effect of Polysaccharide Sulfate (PSS) on contraction or relaxation of rat thoracic endothelium-intact and endothelium-denuded vascular rings and to investigate the underlying mechanisms.METHODS The study was performed with the model of isolated rat thoracic aortic rings in organ bath. The effect of accumulated PSS (0.05～500mg· L^-1) on endothelium-intact aortic rings in resting tension or pre-constricted with KC1, and PSS ( 0.05 ～ 5000 mg· L^-1) on aortic rings pre-constricted with phenylephrine (PE) was observed. When the endothelium of rat thoracic aorta was removed, the effect of accumulated PSS (0.05～500mg·L^-1) on aortic rings in resting tension, pre-constricted with KC1, or pre-constricted with phenylephrine (PE) was observed. In normal or Ca²⁺-free K-H solution, the endothelium-denuded aortic rings were incubated with different concentration of PSS(0.05-500mg·L^-1), examine the effect of certain agents on contraction. When the aortic rings were incubated with phosphoramidone, indomethacin and captopril respectively, the effect of cumulative concentration of PSS(0.05～ 1500 mg·L^-1) on PE pre-constricted endothelium-intact aortic rings was examined. After incubated with PSS (500 mg·L^-1) , the effect of acetylcholine(ACh) on PE pre-constricted endothelium-intact aortic rings was examined.RESULTS Accumulated PSS(0.05-500mg·L^-1) had no significant effects on aortic rings with intact endothelium in resting tension or pre-constricted with KC1. Accumulated PSS (0.05-15 mg·L^-1) had no significant effects on aortic rings with intact endothelium pre-constricted with PE, while accumulated PSS (50-5000 mg·L^-1) enhance the contraction markedly. However accumulated PSS (0.05～500 mg·L^-1) had no significant effects on endothelium-dunuded aortic rings in resting tension or pre-constricted with KC1 and PE. When the endothelium-denuded aortic rings were incubated with PSS (0.05 ～ 500 mg·L^-1) , contraction elicited by cumulatively-added PE or KC1 were not inhibited. Incubation with PSS(500 mg·L^-1) didn't inhibit contraction elicited by KC1 via Ca²⁺ influx or by PE via Ca²⁺ release and Ca²⁺ influx in the endothelium-dunuded aortic rings. When endothelium-intact aortic rings were pre-constricted with PE , endothelin converting enzyme inhibitor phosphoramidone and cyclooxygenase (COX) inhibitor indometacin had no significant effect on the contraction of PSS (50-1500 mg·L^-1) , while angiotensin converting enzyme inhibitor captopril partially inhibited the contraction of PSS (50 ～1500 mg·L^-1) . PSS (500 mg·L^-1) had no effect on the relaxation of ACh in the endothelium-intact aortic rings pre-constricted by PE.CONCLUSION The results indicate that the concentration of PSS from 0.05 to 500 mg·L^-1 didn't have effect on the rat thoracic aortic rings without endothelium in vitro. High concentration (50 ～ 5000 mg·L^-1) of PSS had endothelium-dependent contractile effect on rat thoracic aortas, which may be mediated partially by promoting the synthesis or release of angiotensin â…¡.