Yuan H, Pang S F
Department of Physiology, University of Hong Kong.
Acta Endocrinol (Copenh). 1990 May;122(5):633-9. doi: 10.1530/acta.0.1220633.
The binding of [125I]melatonin, a labelled ligand of melatonin, to quail brain membrane preparations was studied. Kinetic studies indicated that the binding of [125I]melatonin to membrane preparations of quail brains collected at mid-light was time-dependent and reversible. The Kd value determined from kinetic analysis was 614 pmol/l, similar to the Kd 705 +/- 81 pmol/l obtained from saturation experiments. The [125I]melatonin binding sites in quail brain membrane had the following order of pharmacological affinities: melatonin greater than 6-chloromelatonin greater than N-acetylserotonin greater than 5-hydroxytryptamine much greater than 5-methoxytryptophol, tryptamine, L-tryptophan, 5-hydroxytryptophan, 5-hydroxyindole-3-acetic acid, 1-acetylindole-3-carboxaldehyde, 3-acetylindole. Compounds known to act on serotonergic, adrenergic or acetylcholinergic receptors were inactive as compared with melatonin. Our results demonstrated the presence of specific melatonin binding sites in the quail brain membrane preparations. In addition, saturation studies demonstrated that [125I]melatonin binding sites in quail brain membrane preparations were 42% higher at mid-light (39.6 +/- 2.2 fmol/mg protein) than at mid-dark (22.6 +/- 2.5 fmol/mg protein), with no significant variation in their binding affinities.
研究了褪黑素的标记配体[125I]褪黑素与鹌鹑脑膜制剂的结合情况。动力学研究表明，[125I]褪黑素与光期中期采集的鹌鹑脑膜制剂的结合具有时间依赖性且可逆。通过动力学分析确定的Kd值为614 pmol/l，与饱和实验得到的Kd值705±81 pmol/l相似。鹌鹑脑膜中的[125I]褪黑素结合位点具有以下药理学亲和力顺序：褪黑素＞6-氯褪黑素＞N-乙酰血清素＞5-羟色胺＞＞5-甲氧基色醇、色胺、L-色氨酸、5-羟色氨酸、5-羟吲哚-3-乙酸、1-乙酰吲哚-3-甲醛、3-乙酰吲哚。与褪黑素相比，已知作用于血清素能、肾上腺素能或胆碱能受体的化合物无活性。我们的结果证明了鹌鹑脑膜制剂中存在特异性褪黑素结合位点。此外，饱和研究表明，鹌鹑脑膜制剂中的[125I]褪黑素结合位点在光期中期（39.6±2.2 fmol/mg蛋白）比暗期中期（22.6±2.5 fmol/mg蛋白）高42%，其结合亲和力无显著变化。
