LC50 IC50 EC50的区别

LC50———— LC即lethal concentration，即引起试验动物死亡的毒物浓度。表示致死浓度时，常在C的下方写上一具体数字，以表示引起该死亡百分数的浓度，LC50即指引起50％试验动物死亡时的毒物浓度。
EC50————当试验不以死亡作为试验生物对毒物的反应指标，而是观察测定毒物对生物的某一影响，如鱼类失去平衡、畸形、酶活变化及藻类生长受抑制，常用有效浓度即EC（effective concentration）来表示毒物对试验生物的毒性。EC50即指半数有效浓度，是指引起50％试验动物产生某一特定反应，或是某反应指标被抑制一半时的浓度。
% r" n/ ~3 s' ~CC50－－－为致半数细胞毒性所需浓度

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3 _& z; H: c" e' R& F8 c" X3 t来个最简单的：
LC50：半数致死浓度，引起受试对象50%个体死亡的药物浓度。
6 b7 g" E1 c# m' R7 SIC50：半数抑制浓度 ，一种药物能将细胞生长、病毒复制等抑制50%所需的浓度。
EC50：半数效应浓度，引起受试对象50%个体产生一种特定效应的药物剂量。

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IC50TheIC50 is a measure of the effectiveness of a compound in inhibiting biologicalor biochemical function. Often, the compound in question is a drug candidate.This quantitative measure indicates how much of a particular drug or othersubstance (inhibitor) is needed to inhibit a given biological process (orcomponent of a process, i.e. an enzyme, cell, cell receptor or microorganism)by half. In other words, it is the half maximal (50%) inhibitory concentration(IC) of a substance (50% IC, or IC50). It is commonly used as a measure ofantagonist drug potency in pharmacological research. Sometimes, it is alsoconverted to the pIC50 scale (-log IC50), in which higher values indicateexponentially greater potency. According to the FDA, IC50 represents the concentrationof a drug that is required for 50% inhibition in vitro. It is comparable to anEC50 for agonist drugs. EC50 also represents the plasma concentration requiredfor obtaining 50% of a maximum effect in vivo. Determination IC50 of a drugFunctional antagonist assay:The IC50 of a drug can bedetermined constructing a dose-response curve and examining the effect ofdifferent concentrations of antagonist on reversing agonist activity. IC50values can be calculated for a given antagonist by determining theconcentration needed to inhibit half of the maximum biological response of theagonist.IC50 values are dependent onconditions under which they are measured. In general, the higher theconcentration of inhibitor, the more will agonist activity be lowered. IC50value increases as enzyme concentration increases. Furthermore depending on thetype of inhibition other factors may influence IC50 value; for ATP dependentenzymes IC50 value has an interdependency with concentration of ATP, especiallyso if inhibition is all of it competitive. IC50 values can be used to comparethe potency of two antagonists.Competition binding assays:In this type of assay, asingle concentration of radioligand (usually an agonist) is used in every assaytube. The ligand is used at a low concentration, usually at or below its KDvalue. The level of specific binding of the radioligand is then determined inthe presence of a range of concentrations of other competing non-radioactivecompounds (usually antagonists), in order to measure the potency with whichthey compete for the binding of the radioligand. Competition curves may also becomputer-fitted to a logistic function as described under direct fit.In this situation the IC50 isthe concentration of competing ligand which displaces 50% of the specificbinding of the radioligand. The IC50 value is converted to an absoluteinhibition constant Ki) using the Cheng-Prusoff equation (see Ki).IC50 and affinity:IC50 is not a directindicator of affinity although the two can be related at least for competitiveagonists and antagonists by the Cheng-Prusoff eqtn. where Ki is the bindingaffinity of the inhibitor, IC50 is the functional strength of the inhibitor,[S] is substrate concentration and Km is the affinity of the substrate for theenzyme.Whereas the IC50 value for a compound may vary between experimentsdepending on radioligand concentration, the Ki is an absolute value. Ki is theinhibition constant for a drug; the concentration of competing ligand in acompetition assay which would occupy 50% of the receptors if no radioligandwere present.----------------------------------------------------ECx Concentration having aneffect on x% of the population compared to control EC50 " EffectConcentration 50% " or concentration having 50% of effect compared tocontrol LCx concentration havingcaused the death of X% of the population tested compared to control IC50 " InhibitionConcentration 50% " or concentration inhibiting of 50% a parameter likethe growth or luminescence compared to control LC50 concentration havingcaused the death of 50% of the population tested compared to control LD50 " LethalProportions 50% " or proportions having caused the death of 50% of thepopulation tested. ED50  “50%median effective dose”LOEC " Low ObservedEffect Concentration " or concentration with a very weak observableeffect. It is about the lowest concentration for which the effect is differentfrom that of controls. It is the first concentration tested after the NOEC. NOEC " No ObservedEffect Concentration " or concentration without observable effect. It isabout the highest concentration tested for which the effect is significantlynot different from controls

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