摘要
目的模拟失重的尾部悬吊大鼠模型具有限动和抗立位效应两方面的作用。为探讨限动与抗立位效应对大鼠心肌肌原纤维ＡＴＰ酶性能的不同影响及其机制而设计本实验。方法将３０只雄性ＳＤ大鼠分成群居对照组（ＣＯＮ１）、同步对照组（ＣＯＮ２）与４周尾部悬吊模拟失重组（ＳＵＳ）。提纯心肌肌原纤维，用改变反应液中离子强度的方法测定肌原纤维ＡＴＰ酶活性。结果４周模拟失重大鼠心肌肌原纤维相对含量减少。三组大鼠心肌肌球蛋白Ｃａ２＋－ＡＴＰ酶活性的排序为ＣＯＮ１＞ＣＯＮ２＞ＳＵＳ，ＳＵＳ组较ＣＯＮ１组降低９．３％（Ｐ＜０．０５）。ＳＵＳ组的心肌肌原纤维Ｃａ２＋－激活ＡＴＰ酶活性显著低于ＣＯＮ１与ＣＯＮ２组，但ＣＯＮ１与ＣＯＮ２组间无差别。用Ｌｉｎｅｗｅａｖｅｒ－Ｂｕｒｋ作图法测算心肌肌原纤维的Ｃａ２＋亲合常数（Ｋｍ）表明，ＣＯＮ２组的Ｋｍ２与ＳＵＳ组的Ｋｍ３间无差别，ＣＯＮ１组的Ｋｍ１均小于Ｋｍ２和Ｋｍ３，有非常显著性差异（Ｐ＜０．０１）。提示限动可能通过降低心肌肌原纤维对Ｃａ２＋亲合力而降低其ＡＴＰ酶活性；抗立位效应则可能导致心肌肌球蛋白同工酶由Ｖ１向Ｖ３型转化，从而引起ＡＴＰ酶活性降低。结论模拟失重大鼠心肌肌原纤维ＡＴＰ酶活性降低，是?
ObjectiveTail-suspensionpossessestwokindsofeffectonrats:limitedmovementandanti-orthostatic.Thepurposeofpresentstudywastoelucidatethemechanismofefectsoflimitedmovementandanti-orthostaticonfeaturesofmyofibrilATPaseinratmyocardium.MethodsThirtymaleSprague-Dawleyratsweredividedintovivariumcontrol(CON1),synchronouscontrol(CON2)and4weekstail-suspended(SUS)groups.ThemyofibrilsofratleftventricleinthreegroupswerepurifiedandtheactivityofmyofibrilandmyosinATPasewasmeasuredinreactivemediaofdiferentionstrength.ResultsTheresultsshowthatrelativemyofibrilcontentofratleftventriclewasreducedin4weekstail-suspendedgroup.TheCa2+-ATPaseactivityofmyosinwasinCON1>CON2>SUSorder.TheCa2+-ATPaseactivityofmyosinpreparedfromtheleftventricleof4weeksSUSgroupshoweda9.3%decrease(P<0.05)comparedwiththeCON1,whereastheK+-EDTAATPaseactivitydidn'tshowsignificantchangeinthreegroups.TheCa2+-activatedATPaseactivityofmyofibrilsinSUSwasdecreasedcomparedwithCON1orCON2,buttherewasnosignificantdiferencebetweenCON1andCON2.Theafinityconstant(Km)ofmyofibrilstoCa2+wascalculatedbyLineweaver-Burkplot.TherewerenosignificantdiferencebetweenKm2ofCON2groupandKm3ofSUSgroup,buttheKm1ofCON1groupwassignificantlydecreased(P<0.01)comparedwithKm2orKm3.ConclusionItissuggest-edthatthemechanismofdecreaseofATPaseactivityofmyofibrilsinlimitedmovementefectmayin-volvereductionoftheafinityofmyofibrilstoCa2+.ThedecreasedATPaseactivityofmyofibrilinanti-orthostaticefectmaybecausedbyisomyosinofleftventricleshiftingfromV1toV3form.Itisconclud-edthatthedecreaseinATPaseactivityofmyofibrilsofleftventricleinsimulatedweightlessnessratsisduetothecombiningefectsoflimitedmovementandanti-orthostatic.
基金
国家自然科学基金
