Latifpour J, Fukumoto Y, Weiss R M
Section of Urology, Yale University, School of Medicine, New Haven, CT 06510, USA.
Naunyn Schmiedebergs Arch Pharmacol. 1995 Nov;352(5):459-68. doi: 10.1007/BF00169378.
We investigated the binding characteristics of endothelin (ET) receptors in rabbit ureter, bladder dome, bladder base, and urethra and compared the observed receptor properties with those of cloned human ETA and ETB receptors expressed in Chinese hamster ovary K-1 (CHO) cells. Receptor binding experiments with [125I]ET-1 revealed the presence of a single class of specific, saturable, high affinity [125I]ET-1 binding sites in all of the regions of the studied urinary tract. The rank order of the densities (Bmax values) of [125I]ET-1 binding sites was: ureter "bladder dome > bladder base = urethra. ET-1 and ET-2 inhibited [125I]ET-1 binding to the membrane particulates from the various regions of the urinary tract with single high affinity constants. A selective ETA receptor antagonist, BQ 123, and selective ETB agonists, ET-3 and sarafotoxin S6c (STXc), inhibited [125I]ET-1 binding to bladder dome, bladder base, and urethra with high and low affinity constants indicating the presence of both ETA and ETB receptor subtypes in these tissues. The subtype specificity of ET receptors in the rabbit tissues is confirmed with inhibition data obtained from similar binding studies in cloned human ETA and ETB receptors. The proportions of high affinity binding sites for ET-3, representing ETB receptors, were approximately 25%, 27%, and 46% in bladder dome, bladder base, and urethra, respectively. Corresponding values for STXc were approximately 17%, 28%, and 43% in bladder dome, bladder base, and urethra, respectively. In contrast to the findings for ET-3 and STXc, the proportions of high affinity binding sites for BQ 123, representing ETA receptors, in bladder dome, bladder base, and urethra were approximately 84%, 74%, and 60%, respectively. In ureter, these selective compounds inhibited [125I]ET-1 binding with either a low (ET-3 and STXc) or a high binding affinity (BQ 123), suggesting the presence of only a single receptor subtype (ETA) in this tissue. These data indicate that there are regional differences in the density and subtype specificity of ET receptors in the rabbit urinary tract.
我们研究了内皮素（ET）受体在兔输尿管、膀胱顶部、膀胱底部和尿道中的结合特性，并将观察到的受体特性与在中国仓鼠卵巢K-1（CHO）细胞中表达的克隆人ETA和ETB受体的特性进行了比较。用[125I]ET-1进行的受体结合实验表明，在所研究的尿路的所有区域中都存在一类单一的特异性、可饱和、高亲和力的[125I]ET-1结合位点。[125I]ET-1结合位点密度（Bmax值）的顺序为：输尿管＞膀胱顶部＞膀胱底部 = 尿道。ET-1和ET-2以单一的高亲和力常数抑制[125I]ET-1与来自尿路各个区域的膜微粒的结合。一种选择性ETA受体拮抗剂BQ 123以及选择性ETB激动剂ET-3和芋螺毒素S6c（STXc）以高亲和力和低亲和力常数抑制[125I]ET-1与膀胱顶部、膀胱底部和尿道的结合，表明这些组织中同时存在ETA和ETB受体亚型。通过在克隆的人ETA和ETB受体中进行类似结合研究获得的抑制数据，证实了兔组织中ET受体的亚型特异性。代表ETB受体的ET-3高亲和力结合位点的比例在膀胱顶部、膀胱底部和尿道中分别约为25%、27%和46%。STXc在膀胱顶部、膀胱底部和尿道中的相应值分别约为17%、28%和43%。与ET-3和STXc的结果相反，代表ETA受体的BQ 123在膀胱顶部、膀胱底部和尿道中的高亲和力结合位点比例分别约为84%、74%和60%。在输尿管中，这些选择性化合物以低亲和力（ET-3和STXc）或高结合亲和力（BQ 123）抑制[125I]ET-1结合，表明该组织中仅存在单一受体亚型（ETA）。这些数据表明，兔尿路中ET受体的密度和亚型特异性存在区域差异。
