Vasomotor Effect Of Salidrodide On Normal And Exhaustive Rat Mesenteric Artery And Its Regulatory Mechanisms

Vessels are divided into windkessel vessel and peripheral resistance vessel, according to functional characteristics of vessel.The blood vessels affecting peripheral blood flow resistance are collectively known as peripheral resistance vessels, including arteriole, small artery and its branch vessels. The main physiological function of Peripheral resistance vessels refers to diastolic and systolic functions which are regulated by mechanisms of endothelial cell and vascular smooth muscle cell. mechanisms of endothelial cell refer to vasodilatory effect mediated by NO and other vasodilators,while mechanisms of vascular smooth muscle cell refer to the content of Ca2 + in vascular smooth muscle cell regulated by extracellular calcium influx and intracellular calcium release.Peripheral resistance vessels generate resistance to blood flow by the contraction of blood vessels to maintain the normal blood pressure of body. However, peripheral resistance vasomotor dysfunction causes changes of blood pressure, which dose harm to human health directly.The second level branch of rat mesenteric artery belongs to peripheral resistance vessel. It is important to observe vasomotor effect of salidroside on rat mesenteric artery, and explore the underlying regulatory mechanisms.Exhaustive exercise is a pathological state with multi-organ dysfunction, beyond the capacity of body due to the strong and long-lasting exercise load. But whether acute exhaustive exercise can lead to peripheral resistance vascular injury is not clear. By establishing acute swimming exhaustive exercise model,whether acute exhaustive exercise has damage to rat mesenteric artery is observed. As a result, an importantprotective role peripheral resistance vessels play in the body will be clarified.Salidroside(SAL) is one of the main active ingredients of Rhodiola, with anti-hypoxia, anti-oxidative stress, endothelial protection, improving myocardial ischemia, anti-myocardial apoptosis, inhibition of calcium overload, inhibiting global ischemia reperfusion injury, improving nerve cell damage, regulating immune and other pharmacological effects. Salidroside is a new vasoactive drug which can improve the body’s circulation and regulate arterial tension. However, effects salidroside has on peripheral resistance vessels and mechanisms are not known clearly.This study was composed of two aspects:one is that vasomotor effect of SAL on normal rat mesenteric arteryand its regulatory mechanisms,the other is that effect of SAL on acute exhaustive rat mesenteric artery and corresponding mechanisms.Tension was measured by DMT system to evaluate the vasomotor effect of SAL on rat endothelium-intact and endothelium-denuded mesenteric aortic rings, effect of SAL on vasomotor function of intact endothelium mesenteric aortic rings precontracted by KCl, effect of SAL on vasomotor function of endothelium-intact and endothelium-denuded mesenteric artery precontracted by PE in concentration-dependent manner, effect of pre-incubation of N-nitro-L-arginine methylester(L-NAME), methylene blue and indomethacin on relaxation induced by SAL in endothelium intact group, effect of SAL on contraction induced by intracellular Ca2+ release and extracellular Ca2+ influx in endothelium denuded group, changes of vascular tension with ACh acting on the exhaustive rat mesenteric vessel precontracted by PE.effect of SAL on exhaustive rat mesenteric aortic rings pre-incubation by L-NAME and then precontracted by PE.Using enzyme linked immunosorbent assay(ELISA), Influence of SAL on NO or NOS content of rat mesenteric aortic rings was explored.Using Western blot, effects of SAL on the expression of IP3R1 and RyR2 proteins in different groups were found.① SAL(10-8mol·L-1- 10-4 mol·L-1) had significantly vasoconstrictive effect on endothelium-intact mesenteric aortic rings precontracted by KCl(60mmol·L-1)(P<0.05).② SAL relaxed endothelium-intact and endothelium-denuded mesenteric artery precontracted by phenylephrine(1μmol·L-1) in concentration-dependent manner, while the vasodilation of endothelium-intact mesenteric artery was significantly stronger than that of endothelium-denuded one(P<0.05). ③ Pretreatment with L-NAME(0.1mmol·L-1), for 20 min significantly attenuated the vasodilation of endothelium-intact mesenteric artery induced by SAL(P<0.05), while pretreatment with neither indomethacin(0.1mmol·L-1) nor methylene blue(0.1mmol·L-1), for 20 min affected the vasodilation of endothelium-intact mesenteric artery induced by SAL(P>0.05).④By calcium deprivation and calcium addition, SAL relaxed endothelium-denuded mesenteric artery precontracted by phenylephrine(1μmol·L-1)(P<0.05),while SAL had no effect on the increasing tension of mesenteric artery induced by adding CaCl2(P>0.05).⑤AS acetylcholine(ACh(1μmol·L-1)) acted on exhaustive mesenteric vascular precontracted by phenylephrine(PE(1μmol·L-1)), Vasodilation rate of vascular was 84.90% ± 11.42%, which suggests that acute exhaustive rat mesenteric vascular endothelial damage is not obvious. ⑥SAL(10-8mol·L-1- 10-4 mol·L-1) had significantly relexant effect on exhaustive mesenteric aortic rings pre-incubated by L-NAME(0.1mmol·L-1) for 20 min, and then precontracted by PE(1μmol·L-1)(P<0.05).⑦ Using ELISA, SAL(10-4mol·L-1) can significantly increase NO and NOS of mesenteric artery(P<0.05).⑧Using Western blot, compared with the control group,the expression level of IP3R1 protein was significantly lower in SAL group(P <0.01), however,the expression level of RyR2 protein was higher in SAL group(P <0.05). What’s more,In exhaustive swimming group the expression of IP3R1 and RyR2 were both inhibited(P<0.01),While in salidroside group and salidroside-acute exhaustive swimming group, SAL significantly reduced the expression of IP3R1, and increased the expression of RyR2, and the difference was statistically significant(P<0.01)。To summary, ①These results indicate that SAL plays a dual role of vasoconstriction and vasodilation in regulating rat mesenteric artery. Vasoconstriction may be associated with voltage-dependent calcium channel, while vasodilation is relative to the increase of NO released by vascular endothelium and NOS synthesis, meanwhile, vasodilation has relation to inhibiting the expression of IP3R1 and then inhibition of intracellular calcium release in the vascular smooth muscle cells. ② Acute exhaustive rat mesenteric artery keeps relaxant state, which might be associated with compensatory autoregulation or the vitro environment.③ the dominated effect of SAL on acute exhaustive rat mesenteric artery is to relax vessels which is related to inhibiting the expression of IP3R1 and then suppressing intracellular calcium release and possiblely not related to influx of extracellular calcium.