松果体及褪黑素对大鼠胸腺巨噬细胞酪氨酸激酶受体B表达的影响

Effect of pineal gland and melatonin on trkB expression in rat thymus macrophages

目的：研究松果体摘除及补充褪黑素对大鼠胸腺巨噬细胞酪氨酸激酶受体B（trkB）表达的影响。方法：选用2月龄清洁级SD大鼠，分为正常对照组、假手术对照组、松果体摘除组、松果体摘除＋褪黑素注射7．5mg·kg^-1·d^-1组和松果体摘除＋褪黑素腹腔15mg·kg^-1·d^-1组，术后4、8周取材。应用trkB和单克隆抗体EDl免疫荧光双标显色法观察分析松果体摘除及补充外源性褪黑素后胸腺巨噬细胞trkB表达的变化。结果：与对照组相比，松果体摘除术后4周胸腺双阳性细胞表达减弱，补充褪黑素后无变化。术后8周松果体摘除组与对照组相比无明显差异，而低剂量组双阳性细胞表达异常增高，高剂量组恢复正常。各组平均灰度无明显差异。结论：松果体及褪黑素在影响胸腺细胞分化发育过程中，胸腺巨噬细胞表达的trkB也随之发生变化，其与胸腺细胞表达的trkB共同作用参与胸腺细胞分化发育。胸腺神经内分泌微环境的分泌调节是松果体及褪黑素保护胸腺细胞的通路之一。

Objective： To study the effect of pinealectomy （Px） and melatonin （MLT） supplementation upon macrophages tryrosin kinase receptor B （trkB） expression in rat thymus. Methods： The clean 2-month-old rats were divided into five groups： normal control group, sham operation group, pinealectomized group, pinealectomy ＋7.5 mg ·kg^-1·d^-1 MLT intraperitoneal injection group and pinealectomy ＋15 mg·kg^-1·d^-1 MLT intraperitoneal injection group, and their thymus were taken out at 4th week and 8th after operation. Double-immunofluorescent labeling for trkB and ectodermal dysplasia 1 （ED1） antibody was used to observe and analyze the changes of double positive cells in thymus after Px and MLT supplemeritation. Results： Compared to the normal and sham group, the expression of thymic trkB＋ ED1＋ macrophages was weakened at 4th week after Px. MLT supplementation made no difference in the number of double positive cells and positive areas at the same time. But trkB＋ ED1＋ macrophage showed no significant change compared to the normal and sham group at the 8th week after Px, and the expression of macrophages increased significantly in the low dose group at the 8th week, and returned to normal in the high dose group at the 8th week. The average gray scale of double positive cells showed no significant difference among all groups. Conclusion： Macrophage trkB expression of thymic is also infiuenced by pineal gland and MLT, which participate in the differentiation and development of thymocytes with trkB expression. The adjustment of thymus neuroendocine microenvironment is one of the gateways in maintaining the thymocytes by pineal gland and MLT.