Hashemzadeh H, Hollingworth R M, Voliva A
Life Sci. 1985 Aug 5;37(5):433-40. doi: 10.1016/0024-3205(85)90405-9.
3H-Octopamine binds reversibly and with high affinity to sites on adult firefly light organ membranes. The binding is characterized by multiple affinities. Scatchard analysis supported a two site binding model with a tentative Kd value of about 1 nM for the high affinity component. The more abundant lower affinity site had a Kd value of about 60 nM. Guanyl nucleotides (Gpp(NH)p and GTP) greatly reduced the apparent number of octopamine binding sites. Competition studies with known octopaminergic agonists including the formamidine pesticides chlordimeform (CDM) and N-demethyl chlordimeform (DCDM) showed the following rank order of potencies in displacing octopamine: DCDM greater than octopamine = synephrine greater than naphazoline greater than clonidine greater than CDM. It was also observed that phentolamine was much more active than propranolol in antagonizing OA-binding. These relative activities are similar to the abilities of the same compounds to alter adenylate cyclase activity in light organ homogenates. Together with the effect of GTP on binding, these results suggest that the binding sites are functional octopamine receptors of the light organ.
3H-章鱼胺能与成年萤火虫发光器膜上的位点可逆且高亲和力地结合。这种结合具有多种亲和力特征。Scatchard分析支持一个双位点结合模型，其中高亲和力组分的初步解离常数（Kd）值约为1 nM。丰度更高的低亲和力位点的Kd值约为60 nM。鸟苷酸（Gpp(NH)p和GTP）极大地减少了章鱼胺结合位点的表观数量。用已知的章鱼胺能激动剂进行的竞争研究，包括甲脒类农药杀虫脒（CDM）和N-去甲基杀虫脒（DCDM），结果显示在取代章鱼胺方面的效力顺序如下：DCDM > 章鱼胺 = 辛弗林 > 萘甲唑啉 > 可乐定 > CDM。还观察到，酚妥拉明在拮抗章鱼胺结合方面比普萘洛尔活性高得多。这些相对活性与相同化合物改变发光器匀浆中腺苷酸环化酶活性的能力相似。连同GTP对结合的影响，这些结果表明这些结合位点是发光器的功能性章鱼胺受体。
