铅对大鼠脑组织神经生长因子表达的影响及甲状腺激素的调节作用

目的　研究醋酸铅对大鼠脑组织神经生长因子 (NGF)表达的影响及甲状腺激素的调节作用。方法　对SD大鼠用 2 5、5 0、10 0mg/kg体重的醋酸铅腹腔注射 ;用丙基硫氧嘧啶 (PTU)制作甲状腺机能减退大鼠模型 ,再给予 5 0mg/kg体重的醋酸铅 ,分别以免疫组化测定脑组织中NGF蛋白的表达。以放射免疫方法测定血清中三碘甲状腺原氨酸 (T3 )、甲状腺素 (T4)、促甲状腺激素 (TSH)的含量及脑组织中T3 、T4的含量。结果　中、高剂量组皮层组织NGF平均灰度 (180 .4 9± 10 .33、16 9.72±19 .75 )与对照组 (2 0 0 .75± 3.2 7)相比 ,差异有显著性 (P <0 .0 1) ;各剂量组海马组织NGF面密度 (0 .0 8± 0 .14、0 .12± 0 .0 2、0 .13± 0 .0 4 )与对照组 (0 .0 2 5± 0 .0 15 )相比 ,差异有显著性 (P <0 .0 5 )。甲状腺机能减退后再用醋酸铅处理 ,皮层、海马组织NGF面密度和平均灰度未见明显改变。各剂量染铅组大鼠血清中T3 (0 .6 8± 0 .0 2 )、(0 .5 7± 0 .0 4 )、(0 .5 4± 0 .0 2 ) μg/L]和T4(2 8.30± 1.83)、(2 7.35± 2 .5 5 )、(2 4 .0 0± 3.0 1) μg/L]含量明显下降 ,而TSH(6 .34± 1.13)、(7.74± 0 .79)、(9.16± 0 .77)IU]增高 ,与对照组T3 (0 .97± 0 .14 ) μg/L]、T4(5 4 .5 0± 3.70 ) μg/L]和TSH

Effect of lead acetate on the nerve growth factor protein expression and the regulation of thyroid hormone

OBJECTIVES: To study the effect of lead acetate on the expression of nerve growth factor (NGF) protein in rat brain and the regulation of thyroid hormone. METHODS: Lead acetate was given to SD rats intraperitoneally ip. at the dosage of 25, 50 and 100 mg/kg respectively. 6-n-propyl-2-thiouracil (PTU) was used to make a hypothyroid model and then lead acetate was given at the dosage of 50 mg/kg body weight through i.p. The NGF protein expression in rat brain was observed by immunohistochemistry Triiodothyronine (T3), thyroxin (T4), TSH in serum and T3, T4 in brain tissue were determined by radio immunoassays (RIAs). RESULTS: The average gray value of NGF protein in cerebral cortex of 50 mg, 100 mg treated groups (180.49 +/- 10.33, 169.72 +/- 19.75, respectively) were lower than the control (200.75 +/- 3.27, P<0.01). The area density of NGF protein in hippocampus of three treated groups (0.08 +/- 0.14, 0.12 +/- 0.02, 0.13 +/- 0.04, respectively) were significantly different from the control (0.025 +/- 0.015, P<0.05). The area density and the average gray value of NGF protein in lead acetate treated hypothyroid rat brain were of no significant changes. The levels of serum T3 in three treated groups (0.68 +/- 0.02), (0.57 +/- 0.04), (0.54 +/- 0.02) microg/L respectively] and T4 (28.30 +/- 1.83), (27.35 +/- 2.55), (24.00 +/- 3.01) microg/L] in serum were significantly lower while TSH (6.34 +/- 1.13), (7.74 +/- 0.79), (9.16 +/- 0.77) IU] higher than those in the control T3 (0.97 +/- 0.14) microg/L, T4 (54.50 +/- 3.70) microg/L and TSH (4.62 +/- 2.16) IU], and there was a good dose-response relationship. The levels of T3 in cerebral cortex of three treated groups (13.26 +/- 0.81), (11.49 +/- 0.10), (10.42 +/- 1.19) pg/mg pro respectively] and T4 (0.50 +/- 0.03), (0.49 +/- 0.13), (0.42 +/- 0.01) ng/mg pro] were significantly lower than those in control (20.85 +/- 11.01) pg/mg pro, (0.76 +/- 0.14) ng/mg pro, P<0.05, P<0.01]. CONCLUSION: Lead could increase the NGF protein expression in rat brain, which may be regulated by thyroid hormone.