Duncan M J, Heller K S, Purvis C C, Massey B T, Stetson M H
Department of Anatomy and Neurobiology, University of Kentucky, Chandler Medical Center, Lexington 40536-0084.
Brain Res. 1993 Dec 17;631(1):107-13. doi: 10.1016/0006-8993(93)91193-v.
These studies used quantitative in vitro autoradiography to investigate whether endogenous or exogenous melatonin modulate specific 2-[125I]iodomelatonin binding sites in the pars tuberalis or suprachiasmatic nuclei of Siberian hamsters. Saturation analyses were conducted on tissue sections from hamsters that were pinealectomized, exposed to constant illumination (72 h), or injected with melatonin, and from hamsters that were treated as controls. High affinity (Kd approximately 20-75 pM) specific 2-[125I]iodomelatonin binding sites were detected in the suprachiasmatic nuclei and pars tuberalis of all animals. Neither pinealectomy nor constant illumination significantly affected either the affinity or the density of the specific 2-[125I]iodomelatonin binding sites in either region. Melatonin injections led to a decrease in specific 2-[125I]iodomelatonin binding to the pars tuberalis at 3-4 h after the last injection. However, washing the sections before incubation with 2-[125I]iodomelatonin eliminated this effect, suggesting that melatonin was occupying the binding sites rather than decreasing their actual number. Furthermore, when hamsters were sacrificed 18 h after the last melatonin injection, no effect of melatonin on either the affinity or density of specific 2-[125I]iodomelatonin sites was observed. These data suggest that 2-[125I]iodomelatonin binding sites in Siberian hamsters are not regulated by changes in circulating melatonin levels.
这些研究使用定量体外放射自显影术来调查内源性或外源性褪黑素是否调节西伯利亚仓鼠结节部或视交叉上核中特定的2-[125I]碘褪黑素结合位点。对松果体切除、持续光照(72小时)或注射褪黑素的仓鼠以及作为对照处理的仓鼠的组织切片进行饱和分析。在所有动物的视交叉上核和结节部均检测到高亲和力(解离常数约为20 - 75皮摩尔)的特定2-[125I]碘褪黑素结合位点。松果体切除和持续光照均未显著影响任一区域中特定2-[125I]碘褪黑素结合位点的亲和力或密度。褪黑素注射导致在最后一次注射后3 - 4小时,特定2-[125I]碘褪黑素与结节部的结合减少。然而,在用2-[125I]碘褪黑素孵育前洗涤切片消除了这种效应,这表明褪黑素占据了结合位点而非减少其实际数量。此外,当在最后一次注射褪黑素18小时后处死仓鼠时,未观察到褪黑素对特定2-[125I]碘褪黑素位点的亲和力或密度有任何影响。这些数据表明,西伯利亚仓鼠中的2-[125I]碘褪黑素结合位点不受循环褪黑素水平变化的调节。