骨癌痛大鼠脊髓脑啡肽表达的变化

The change of enkephalin in the spinal cord in rats with bone cancer pain

目的观察脊髓脑啡肽在大鼠骨癌痛中的表达变化。方法雌性未交配Wistar大鼠72只，体重160-180g，随机均分为两组：骨癌痛组（B组）和空白对照组（C组）。B组制成骨癌痛模型，c组为假手术组，B组和C组分别在左胫骨中上端注射Walker256乳腺癌细胞2×10^5个或PBS液，体积为10μl。所有大鼠于术前1d、术后7、14、21d时测定机械痛阈和左后肢抬足时间。大鼠行影像学检测判定其胫骨骨质破坏情况。两组于术后7、14、21d各取12只大鼠分别处死，取左侧胫骨作HE染色，组织学鉴定肿瘤生长及骨质破坏的程度；取腰膨大L4～L6脊髓组织，采用逆转录一定量聚合酶链反应（RT-PCR）测定前脑啡肽原（PENK）mRNA表达情况和放射免疫法（EusA）检测脊髓组织中亮氨酸脑啡肽（L-EK）的含量变化。结果与C组比较，B组术后7、14、21d机械痛阈进行性下降（P〈0．01），左后肢抬足时间进行性延长（P〈0．01）。与C组比较，B组术后7d脊髓PENKmRNA和L-EK增加，14、21d脊髓PENKmRNA和L-EK逐渐减少（P〈O．01）。结论脊髓脑啡肽的表达在大鼠骨癌痛中明显变化，推测脊髓脑啡肽在骨癌痛产生和维持中起重要作用。

Objective To investigate the expression of enkephalin in the spinal cord of rats with bone cancer pain. Methods Seventy-two female wistar rats without mating were randomly divided into two groups： a model group（group B）, 2 × 10^5 cells in 10 μl PBS were injected into the left tibia of rats; and a sham group （group C）, only 10 μl PBS injected into the left tibia of rats. Spontaneous lifting duration and mechanical withdrawal threshold of the hind paw of rats were measured before operation and on day 7, 14 and 21 after operation. The development of the bone tumor and structural damage to the bone was monitored by X line. The animals in two groups were killed on day 21; in two groups were sacrificed at days 7,14 and 21. The left tibia bones from all the rats were stained with HE and segments of lumbar spinal cord were taken to detected proenkephalin mRNA with RT-PCR and enkephalin using radioimmunoassay. Results Compared with group C, the value of mechanical pain thresholds on days of 7, 14 and 21 were significantly decreased in group B; and the value of spontaneous lifting duration were significant increased. The expression of proenkephalin mRNA and enkephalin in the spinal cord was upregulated at day 7, but gradually decreased. Conclusion The expression of enkephalin in the spinal cord in bone cancer pain upregulated significantly suggesting it may participate in generation and maintenance of the pain from bone cancer.