摘要
应用放射配体结合分析证实鸟类（鸡、鸭、鸽子和鹌鹑）的胸腺上存在［（１２５）Ｉ］降黑素（Ｍ）特异结合位点。这些结合位点具有以下特点：低结合容置，高亲和力，对Ｍ有高度特异性；其结合是稳定的、可逆的及可饱和的，符合特异结合位点的全部条件。光中期的特异结合量明显高于暗中期，表明胸腺降黑素受体（ＭＲ）存在昼夜节律。亚细胞分布的研究显示ＭＲ最大结合在胸腺细胞核，线粒体次之。与年龄关系的研究显示出生时最高，１２周明显降低，２０周降低更显著，表明ＭＲ存在年龄依赖性降低。证实鸟类胸腺存在ＭＲ，是Ｍ作用的靶器官；提示Ｍ对免疫系统的调节是直接作用的结果。
Melatonin binding sites in the membrane preparations of the thymus of birds, including chickens, ducks, pigeons and quails, were studied with 2-[(125)I]iodomelatonin ([(125)I]M)as a radioligand.The binding sites were stable, saturable, reversible and of high affinity. Maximum binding capacity (Bmax) was 0.97±0.15,0.98±0.14,0.83±0.11,0.57±0.12 fmol/mg of protein at mid-light and 0.57±0.14,0.69±0.11,0.42±0.13,0.39±0.08 fmol/mg of protein at mid-dark,respectively, which indicated that a circadian rhythm in [(125)I]M binding sites was present in the birds thymus. The subcellular distribution of binding sites in the birds thymus was in the following descending order:neuclear,mitochondrial,microsomal and cytosolic fraction.Specificity studies indicated that the binding sites were highly specific for melatonin.There was an age-related decrease in [(125)I]M binding sites of thymus membranes with higher densities in the neonate. The findings demonstrate that [(125)I]M binding sites are present in the birds thymus, which is a target organ of melatonin and thus melatonin exerts a direct effect on the immune system.
出处
《标记免疫分析与临床》
CAS
1996年第1期20-23,28,共5页
Labeled Immunoassays and Clinical Medicine
关键词
降黑素
激素
受体
胸腺
鸟类
Melatonin binding sites/melatonin Receptors, endogenous substances Thymus Birds
