Ripodas A, De Juan J A, Moya F J, Fernandez-Cruz A, Fernandez-Durango R
Diabetes, Hypertension, and Obesity Unit, Department of Internal Medicine, Hospital Universitario San Carlos, Madrid, 28040, Spain.
Exp Eye Res. 1998 Jan;66(1):69-79. doi: 10.1006/exer.1997.0405.
The endothelins are important vasoactive ocular peptides and there is some evidence that they may modulate intraocular pressure. We investigated the existence and localization of endothelin receptor subtypes using subtype selective ligands in rat ciliary body. Scatchard transformation of saturation binding experiments revealed that the KD and Bmax for [125I]ET-1 and [125I]ET-3 to membranes from ciliary body were 41.7+/-9 pM and 236+/-20 fmol mg-1 protein and 37. 8+/-0.4 pM and 160+/-2.0 fmol mg-1 protein, respectively. Competitive experiments in the presence of cyclic pentapeptide BQ123 (selective for ETA receptors) and BQ3020 (selective for ETB receptors), demonstrated the existence of ETA and ETB receptors in a ratio of 35:65. Cross-linking of [125I]ET-1 and [125I]ET-3 to ciliary body membranes resulted in the labeling of two bands with apparent molecular masses of 52 and 34 kDa, suggesting that ETA and ETB receptors have similar molecular mass. The 34 Kda band is a proteolytic degradation product of the 52 Kda band. Autoradiographic results show that specific [125I]ET-1 binding sites, displaced by BQ123 and BQ3020, are localized to the ciliary epithelium, supporting the idea that ETA and ETB subtype receptors exist in this tissue.
内皮素是重要的血管活性眼肽，有证据表明它们可能调节眼压。我们使用亚型选择性配体研究了大鼠睫状体中内皮素受体亚型的存在和定位。饱和结合实验的Scatchard转换显示，[125I]ET-1和[125I]ET-3与睫状体膜的KD和Bmax分别为41.7±9 pM和236±20 fmol mg-1蛋白以及37.8±0.4 pM和160±2.0 fmol mg-1蛋白。在环五肽BQ123（对ETA受体有选择性）和BQ3020（对ETB受体有选择性）存在下的竞争性实验表明，ETA和ETB受体以35:65的比例存在。[125I]ET-1和[125I]ET-3与睫状体膜的交联导致标记出两条表观分子量分别为52 kDa和34 kDa的条带，表明ETA和ETB受体具有相似的分子量。34 kDa条带是52 kDa条带的蛋白水解降解产物。放射自显影结果表明，被BQ123和BQ3020取代的特异性[125I]ET-1结合位点定位于睫状体上皮，支持了该组织中存在ETA和ETB亚型受体的观点。
