低剂量电离辐射对小鼠下丘脑和免疫器官POMC转录水平的影响

Effect of low dose radiation on POMC transcription level in mouse hypothalamus and immune organs

目的观察７５ｍＧｙＸ射线全身照射后小鼠下丘脑和免疫器官ＰＯＭＣ转录水平的变化。方法地高辛标记碱性磷酸酶显色原位杂交。结果假照组下丘脑和免疫器官即有ＰＯＭＣ转录水平的表达，且下丘脑主要定位弓状核。７５ｍＧｙ全身照射后下丘脑ＰＯＭＣｍＲＮＡ含量减少，１小时内降低明显，１２小时仍在继续下降。免疫器官ＰＯＭＣｍＲＮＡ含量在照射后逐步增加，８小时达顶点，而后开始回降。脾脏变化最明显。结论低剂量电离辐射照射后下丘脑ＰＯＭＣ的减少可能是下丘脑－垂体－肾上腺皮质（ＨＰＡ）轴功能下调的直接原因，从而诱发免疫功能增强。

Objective\ To disclose the changes in mRNA transcription level of POMC in the hypothalamus and immune organs after low dose radiation.Method\ In situ hybridization was used to examine the changes of POMC mRNA transcription level in mouse hypothalamus and immune organs following whole body irradiation (WBI) with 75mGy X rays.Results\ There was a basal expression of POMC mRNA in both the hypothalamus and immune organs.POMC mRNA positive neurone were located in the arcuate nucleus of hypothalamus.WBI with 75mGy X rays could significantly down regulate the POMC transcription level that was remarkable within 1h and remained low in the observation period of 12h.POMC transcription level in mouse immune organs increased with time within 8h after irradiation and then began to decrease but still remained at a higher than normal level.The changes of POMC transcription level were more marked in the spleen than in other immune organs.Conclusion\ These findings suggest that the immediate decrease of POMC transcription level in the hypothalamus might be the direct cause of the down regulation of the hypothalamus pituitary adrenocortical axis after WBI with 75mGy X rays,accompanied with an increase in POMC transcription in immune organs.