Pang C S, Brown G M, Tang P L, Cheng K M, Pang S F
Clarke Institute of Psychiatry, Toronto, Canada.
Biol Signals. 1993 Jul-Aug;2(4):228-36. doi: 10.1159/000109496.
The pineal gland plays an important role in seasonal adaptation including variation in energy requirement. Animals exhibiting seasonal changes in their energy expenditure would be benefited if their cardiac and pulmonary systems respond to the pineal photoperiodic signal, melatonin, appropriately. Thus, we would like to hypothesize that melatonin receptors are present in the heart and lung. Using a specific labeled melatonin agonist, 2-[125I]iodomelatonin, binding sites were demonstrated in the lung and heart of birds and other animals. In the chicken lung, there were high affinity (equilibrium dissociation constant, Kd = 9.11 +/- 0.73 pmol/l) and low density (maximum number of binding sites, Bmax = 1.29 +/- 0.16 fmol/mg protein) 2-[125I]iodomelatonin binding sites that were highly specific to melatonin. Similar binding with lower density was demonstrated in the quail and frog lungs. In the duck heart, specific 2-[125I]iodomelatonin binding sites with a Kd of 30.5 +/- 3.5 pmol/l and a Bmax of 0.46 +/- 0.1 fmol/mg protein (n = 4) were demonstrated. Competitive studies suggested that these binding sites were specific to melatonin. Thus, saturable and reversible 2-[125I]iodomelatonin binding was present in the lung and heart membrane preparations of birds and possibly other animals. The picomolar affinity, femtomolar density and highly specific pharmacological profile of these binding sites suggest that they can be classified as ML-1 melatonin receptors. The 2-[125I]iodomelatonin binding sites described in the lung and heart as well as those binding sites demonstrated in other peripheral tissues suggest the ubiquitous direct action of melatonin on peripheral tissues.
松果体在包括能量需求变化在内的季节性适应中发挥着重要作用。如果动物的心脏和肺部系统能对松果体光周期信号褪黑素做出适当反应，那么能量消耗呈现季节性变化的动物将从中受益。因此，我们推测心脏和肺中存在褪黑素受体。使用一种特异性标记的褪黑素激动剂2-[¹²⁵I]碘褪黑素，在鸟类和其他动物的肺和心脏中证实了结合位点的存在。在鸡肺中，存在高亲和力（平衡解离常数，Kd = 9.11±0.73 pmol/L）和低密度（最大结合位点数，Bmax = 1.29±0.16 fmol/mg蛋白质）的2-[¹²⁵I]碘褪黑素结合位点，这些位点对褪黑素具有高度特异性。在鹌鹑和青蛙的肺中也证实了类似但密度较低的结合情况。在鸭心脏中，证实了特异性的2-[¹²⁵I]碘褪黑素结合位点，其Kd为30.5±3.5 pmol/L，Bmax为0.46±0.1 fmol/mg蛋白质（n = 4）。竞争性研究表明这些结合位点对褪黑素具有特异性。因此，在鸟类以及可能其他动物的肺和心脏膜制剂中存在可饱和且可逆的2-[¹²⁵I]碘褪黑素结合。这些结合位点的皮摩尔亲和力、飞摩尔密度和高度特异性的药理学特征表明它们可被归类为ML-1褪黑素受体。在肺和心脏中描述的2-[¹²⁵I]碘褪黑素结合位点以及在其他外周组织中证实的那些结合位点表明褪黑素对外周组织具有普遍的直接作用。
