甲状腺功能低下大鼠仔鼠大脑皮质中NO及NOS活性的变化

目的　观察甲状腺功能低下大鼠仔鼠大脑皮质中一氧化氮 (NO)含量 ,一氧化氮合酶 (NOS)活性和环鸟苷酸 (cGMP)含量的变化 ,为探讨甲状腺激素对神经系统发育的作用机制 ,提供实验资料。方法　取怀孕 3日的SD大鼠 10只 ,随机分为实验组与对照组。实验组饮含 0 1%高氯酸钠的自来水 ,对照组饮自来水直至仔鼠产下 15日 ,其产下的仔鼠分别为甲状腺功能低下仔鼠及正常仔鼠。用放射免疫法测定仔鼠血清中游离三碘甲腺原氨酸 (FT3 )、游离四碘甲腺原氨酸 (FT4)、促甲状腺激素 (TSH)和cGMP含量 ,采用硝酸还原酶法测仔鼠大脑皮质中NO含量 ,采用分光光度计法测NOS活性。结果　 15日龄甲低组仔鼠血清FT3 、FT4含量较对照组明显降低 (P <0 0 1) ,而血清TSH含量较对照组明显增高 (P <0 0 1)。实验组仔鼠大脑皮质中NO含量、NOS活性及cGMP含量较对照组显著降低 (P <0 0 1)。相关分析表明 :血清FT3 含量与大脑皮质中NO、cGMP含量呈显著正相关 ,r值分别为 0 91、 0 97,P <0 0 1。血清FT4含量与大脑皮质中NO、cGMP含量也呈显著正相关 ,r值分别为 0 90、 0 96 ,P <0 0 1。大脑皮质中NO含量与cGMP含量呈显著正相关 ,r值为 0 90 ,P <0 0 1。血清TSH与大脑皮质中NO、cGMP含量呈显著负相关 ,r值分别为 - 0 86、 - 0 8

Changes of NO and NOS in the Cortex of Neonated Hypothyroid Rat

Objective To observe nitric oxide(NO)contents,nitric oxide synthase (NOS)activity and cyclic guanina monophosphate(cGMP)contents in the cortex of neonated hypothyroid rats.Methods Ten SD rats were divided randomly into hypothyroid group and control group.The animals had drunk water with 1% sodium perchlorate and normal water respectively from the 3th embryonic day to the 15th day after childbirth.The neonated rats were perinatal hypothyroidism and normal neonated rats respectively.FT 3,FT 4,TSH and cGMP contents were measured with radioimmunoassay.NOS activity and NO contents were assassed with spectrophotometric analysis.Results The serum FT 3,FT 4,and TSH decreased significantly in hypothyroid rats as compared to that in normal controls( P <0 01) The NO,NOS and cGMP contents of the cortex of neonated rats were lower in hypothyroidism rats than those in controls ( P <0 01) The correlation between serum FT3 and cortex NO and cGMP and the correlation between serum FT4 and cortex NO and cGMP were both positive significantly ( P <0 01) There was a positive correlation between cortex NO and cGMP( P <0 01).But a negative correlation between serum TSH and cortex NO and cGMP could be observed ( P <0 01).Conclusions The decline of thyroid hormone can decrease the contents of NO and cGMP in the neonatal rat cortex.NO/cGMP signaling pathway may play an important role in the course of brain development regulated by thyroid hormone.