松果体切除对鸡腔上囊2－［^（125）I］褪黑素特异结合位点昼夜节律的影响

Pinealectomy affects the diurnal variations in 2-[~(125]I]-labelled iodomelatonin binding sites in chicken bursa of fabricius

本研究探讨松果体切除对鸡腔上囊２－［^（１２５）Ｉ］褪黑素特异结合容量及亲和力昼夜节律的影响。切除２ｄ龄小鸡的松果体（实验组），６周时分别在光中期和暗中期将手术组和对照组（假手术组）各７只鸡断头处死。结果：对照组鸡腔上囊２－［~１２５Ｉ］褪黑素结合容量光中期（３．７５±０．３９ｆｍｏｌ／ｍｇ蛋白）高于暗中期（１．０８±０．２０ｆｍｏｌ／ｍｇ蛋白）；手术组鸡腔上囊褪黑素特异结合容量在光中期低于对照组。松果体切除破坏了循环褪黑素的昼夜节律以及２─［~１２５Ｉ］褪黑素特异结合容量的昼夜节律，而亲和力无明显变化（Ｐ＞０．０５）。提示鸡腔上囊褪黑素特异结合位点的昼夜节律是通过松果体分泌的内源性褪黑素调节的。此外，在鸟类发育的早期阶段切除松果体可以降低褪黑素特异结合位点的结合容量。

The diurnal variations of 2-[￣125Ⅱ] iodomelatonin binding densities and affinities in the bursa of pinealectomized and sham-operated chickens were studied.The pineals of 2-dayold chickens were removed,and 7 chickens from cach group were decapitated at 6 weeks of age. The diurnal variations of 2-[￣125Ⅱ] iodomelatonin binding site density in the bursa of the sham-operated chicken remained significant (P<0.05) with a higher value at midlight (3.75 ±0.39 fmol/mg protein) than at middark (1.08±0.20 fmol/mg protein). Pinealectomy disturbed the diurnal rhythm of circulating melatonin and the density of 2-[￣125Ⅱ] iodomelatonin binding site density in the chichen bursa, but there was no significant change (P>0.05) in the Kd value. The densities of the bursal melatonin binding sites at midlight in the pinealectomized chickens were lower than that of the sham-operated chickens. Our results suggested that the circadian variations of 2-[￣125Ⅱ] iodomelatonin binding sites in the chicken bursa is regulated by pincal melatonin. In addition, pinealectomy in the early stage of development can damp the capacity of 2-[￣125Ⅰ] iodomelatonin binding.