The Effects Of MS23 On Isolated Rat Thoracic Aorta

OBJECTIVE To study the mechanisms of MS23 on vessel smooth muscle cell by means of the observation of MS23 and the combinations of MS23 with endothelium, endothelium-denuded and N-nitro-L-arginine methylester(L- NAME) on high K⁺-contracted or norepinphrine(NE)-contracted the isolated rat thoracic aorta rings and the analysis of the function of endothelium and NO on this experiment. METHODS The effects of the drugs on rat isolated thoracic aortic rings' contraction induced by KCl with different consistencies or by norepinphrine(NE) were observed with MS4000 computer system. The rings were isolated from Wistar rats which were 250-280 grams heavy. RESULTS 1. MS23 can relax the resting tone of the isolated rat thoracic aortic rings at high consistency(3×10^-5 mmol/L and 1×10^-4 mmol/L). 2. MS23 produced respectively relaxations about 1.60±0.40g(P<0.01),1.51±0.11g (P<0.01) of the high K⁺-contraction(60mmol/L) and norepinphrine(NE)-contraction (1×10^-5 mol/L) on aortic rings of rats. 3. The relaxations to KCL are progressive enhancing with the increasing consistency of MS23. The percentage of contraction of KCL(70mmol/L) is only 9.19±10.29% when the consistency of MS23 is 10^-4 mmol/L . And, the quantity-effect curve of KCL moves right and down and the EC50 of KCL were growing with the consistency of MS23 increasing. 4. The effect of MS23 on the aortic rings of rats has no business with the function of endothelium. 5. L-NAME (or NO) does not change the function of MS23 in this experiment. 6. MS23 may be a special PDE4 inhibitor. CONCLUSION MS23 can decrease the resting tone of the isolated rat thoracic aortic rings at high consistency. MS23 showed relaxations on the high K+-contraction or norepinphrine(NE)-contraction and the relaxations are progressive weakening with consistency increasing. The function of endothelium and the role of L-NAME or NO do not change the relaxations of MS23 on the isolated aortic rings from rats. MS23 may be a special PDE4 inhibitor.