Raffa R B, Schupsky J J, Jacoby H I
R.W. Johnson Pharmaceutical Research Institute, Spring House, Pennsylvania, USA.
J Pharmacol Exp Ther. 1996 Feb;276(2):647-51.
Endothelins (ET-1, ET-2 or ET-3) or endothelin precursors (big-ET-1[1-38], big-ET-2[1-37] or big-ET-3[1-41]) injected i.p. in mice have previously been shown to elicit a characteristic nociceptive behavioral response. In this study, we investigated the endothelin receptor type (ETA or ETB) that mediates this behavioral response. Mice were injected i.p. with ET-1, ET-2, ET-3, big-ET-1[1-38], big-ET-2[1-37], big-ET-3[1-41], sarafotoxin S6a, sarafotoxin S6b, sarafotoxin S6c, ET-1 with Ala substitutions for Cys3 and Cys11 or His-Leu-Asp-Ile-Ile-Trp, and quantal dose-response curves were obtained for each of the compounds (except the latter). Co-administration of enzyme inhibitors with the big-endothelins was used to establish the requisite conversion to endothelins and big-ET-1[22-38], big-ET-2[22-37] and ET-3[22-41] amide, and the ETA-selective antagonist cyclo[-D-Asp-Pro-D-Val-Leu-D-Trp-] was used to determine receptor specificity. The ED50 values were 2.9, 3.3 and 23.9 micrograms/kg i.p. for ET-1, ET-2 and ET-3, respectively, 0.6, 0.6 and 13.1 micrograms/kg i.p. for sarafotoxin S6a, sarafotoxin S6b and sarafotoxin S6c, respectively, and 5.3 micrograms/kg i.p. for ET-1 with Ala substitutions for Cys3 and Cys11. Big-ET-1[22-38], big-ET-2[22-37], big-ET-3[22-41] amide and ET-C produced less than 25% effect up to 2000 micrograms/kg. The big-ET-1-induced effects were blocked by the enzyme inhibitors phosphoramidon and thiorphan (ID50 = 0.9 mg/kg) but not by ubenimex (bestatin), captopril or perindopril. Cyclo[-D-Asp-Pro-D-Val-Leu-D-Trp-] blocked ET-1- and ET-2-induced effects but not ET-3-, ACh- or phenyl-p-quinone-induced effects. These results suggest that endothelin-induced nociceptive behavioral response in mice can be mediated via both ET receptor types, ETA and ETB. Further, the ET-1 carboxy-terminal hexapeptide is insufficient to produce the effect, and the Cys3-Cys11 disulfide bridge of ET-1 is not required.
先前已表明，腹腔注射内皮素（ET-1、ET-2或ET-3）或内皮素前体（大ET-1[1-38]、大ET-2[1-37]或大ET-3[1-41]）可引发特征性的伤害感受行为反应。在本研究中，我们调查了介导这种行为反应的内皮素受体类型（ETA或ETB）。给小鼠腹腔注射ET-1、ET-2、ET-3、大ET-1[1-38]、大ET-2[1-37]、大ET-3[1-41]、蛙皮毒素S6a、蛙皮毒素S6b、蛙皮毒素S6c、用丙氨酸替代Cys3和Cys11的ET-1或His-Leu-Asp-Ile-Ile-Trp，并为每种化合物（后者除外）获得了剂量-反应曲线。将酶抑制剂与大内皮素共同给药以确定向内皮素以及大ET-1[22-38]、大ET-2[22-37]和ET-3[22-41]酰胺的必要转化，并且使用ETA选择性拮抗剂环[-D-Asp-Pro-D-Val-Leu-D-Trp-]来确定受体特异性。ET-1、ET-2和ET-3腹腔注射的半数有效剂量（ED50）值分别为2.9、3.3和23.9微克/千克，蛙皮毒素S6a、蛙皮毒素S6b和蛙皮毒素S6c腹腔注射的ED50值分别为0.6、0.6和13.1微克/千克，用丙氨酸替代Cys3和Cys11的ET-1腹腔注射的ED50值为5.3微克/千克。高达2000微克/千克时，大ET-1[22-38]、大ET-2[22-37]、大ET-3[22-41]酰胺和ET-C产生的效应小于25%。大ET-1诱导的效应被酶抑制剂磷酰胺脒和硫磷酰胺阻断（半数抑制剂量（ID50）=0.9毫克/千克），但不被乌苯美司（抑肽酶）、卡托普利或培哚普利阻断。环[-D-Asp-Pro-D-Val-Leu-D-Trp-]阻断ET-1和ET-2诱导的效应，但不阻断ET-3、乙酰胆碱或对苯醌诱导的效应。这些结果表明，内皮素诱导的小鼠伤害感受行为反应可通过ETA和ETB两种受体类型介导。此外，ET-1的羧基末端六肽不足以产生该效应，并且ET-1的Cys3-Cys11二硫键并非必需。
