钙增敏效应参与急性缺氧介导的猪冠状动脉收缩反应OA

AIM:Acute hypoxia can induce transient contraction of coronary arteries,leading to myocardial ischemia and even cardiac dysfunction.However,the precise regulatory mechanisms remain unclear.In this study,we ap-plied various interventions to isolated porcine coronary arteries by modulating cytoplasmic calcium concentrations mediated by calcium channels on the plasma membrane and sarcoplasmic reticulum,aiming to investigate the relationship between hypoxic contraction and intracellular calcium levelsaswell as calcium sensitization effects.METHODS:Isolated rings of the porcine left anterior descending coronary artery served as the experimental model.Based on distinct intervention tar-gets,four core experimental groups were established.The specific grouping,sample size(n)for each group,and treat-ments were as follows:(1)nitric oxide(NO)-soluble guanylyl cyclase(sGC)pathway and energy metabolism intervention groups including control(n=5),nitric oxide synthase inhibitor nitro-L-arginine(NLA,10-4 mol/L;n=4 to 5),soluble guanylyl cyclase(sGC)antagonist 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one(ODQ,3×10-5 mol/L;n=5),endothe-lium-denuded(n=5),normal glucose incubation(n=3),and glucose-free incubation(n=3)groups;(2)calcium source intervention groups including normal calcium control(n=4),calcium-free incubation with 5×10-3 mol/L ethylene glycol tet-raacetic acid(EGTA;n=4),L-type calcium channel antagonist nifedipine(10⁻⁶ mol/L;n=5 to 7),non-selective cation channel inhibitor NiCl2(5×10-5 mol/L;n=5 to 7),sarcoplasmic reticulum Ca²⁺-ATPase inhibitor thapsigargin(2×10-6 mol/L;n=5 to 7),and inositol trisphosphate(IP3)receptor antagonist 2-aminoethoxydiphenyl borate(2-APB,10-4 mol/L;n=5 to 7)groups;(3)myosin light chain kinase(MLCK)pathway intervention groups including control(n=4)and MLCK-specific inhibitor 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride(ML-7,10-5 mol/L;n=6)groups;(4)myosin light chain phosphatase(MLCP)activity and endothelium-dependence intervention groups including endothelium-intact(n=4)and mechanically endothelium-denuded(n=6)groups.All arterial rings were pre-contracted with either U46619(3×10-7 mol/L)or KCl(6×10-2 mol/L)and then subjected to 10 minutes of hypoxia(95%N2+5%CO2).Changes in vascular tension were continuously monitored and recorded using a multi-channel physiological signal acquisition system.Furthermore,combined with Western blotting,the phosphorylation level of myosin light chain(MLC)and the activity of MLCP were determined;the phosphorylation levels of MLC and MLCP were also compared between en-dothelium-intact and endothelium-denuded coronary arteries under hypoxic conditions.RESULTS:(1)Hypoxic constric-tion of porcine coronary arteries is dependent on the activation of endothelium-derived nitric oxide(NO)and sGCin vascu-lar smooth muscle cells.(2)Hypoxic contraction in porcine coronary arteries is independent of extracellular Ca2+influx.(3)Hypoxic contraction in porcine coronary arteries does not rely on intracellular Ca2+release from the sarcoplasmic reticu-lum.(4)Hypoxic contraction in porcine coronary arteries leads to inhibition of myosin light chain phosphatase activity,suggesting increased calcium sensitization in coronary artery smooth muscle.CONCLUSION:The mechanism under-lying acute hypoxia-induced vasoconstriction exhibits distinct characteristics:it does not rely on extracellular calcium in-flux mediated by plasma membrane calcium channels,nor is it associated with intracellular calcium mobilization from sar-coplasmic reticulum stores.Instead,it is mediated by a significant enhancement in calcium sensitivity regulated by myo-sin light chain phosphatase,a process referred to as calcium sensitization.