Study of osmoregulation in birds

长期以来，关于β受体对β受体的调节作用尚不清楚。近年来，水通道蛋白4（aquaporin 4，AQP4）被认为是一种新型的神经递质受体，但目前还没有明确的证据。本研究克隆了鸡AQP4基因的cDNA并测定了其序列。本研究分析了AQP4基因在鸡下丘脑中的表达及其与神经刺激的关系。AQP4基因在高渗环境中表达增加。因此，AQP4可能与鸡的AQP4受体有关。由于在哺乳动物中没有观察到AQP4基因表达随高渗而增加的现象，因此这种增加在鸡中是特有的，比较蛋鸡和肉仔鸡品系在禁水后精氨酸催产素（AVT）基因的表达，两种品系的鸡体重均下降，血浆渗透压均升高。在AVT基因表达方面，蛋鸡AVT基因表达量增加，而肉鸡AVT基因表达量没有增加。这些结果表明，两种品系的摄食调节机制不同，神经肽Y（NPY）可能在摄食行为中起重要作用。但是，在水剥夺后，NPY基因的表达在鸡增加。因此，这些数据表明，神经肽Y在鸡体内的水平衡中具有关键作用。

For long time, it has been not clear about the osmoreceptor on the osmoregulation. Recently, aquaporin 4(AQP4) has been a candidate as an osmoreceptor, but there are no clear evidence about that. We cloned chicken AQP4 cDNA and determined its sequence. We analyzed the gene expression of AQP4 in the chicken hypothalamus in related with osmostimulation. AQP4 gene expression in the chicken increased by hyperosmolality. Threrefore, these results suggest that AQP4 may involve osmoreceptor in the chicken. Since there are no observations about the increase of AQP4 gene expression by hyperosmolality in the mammals, such increase is specific thing in the chicken.Comparing arginine vasotocin(AVT) gene expression between layer and broiler strain after water deprivation, both strains chick decreased body weights and increased plasma osmolality. On AVT gene expression, AVT gene expression increased in layer but not in broiler. These results suggested that there was some different mechanism of osmoregulation between two strains.It has been considered that neuropeptide Y(NPY) is a important role for feeding behavior. But, after water deprivation, NPY gene expression increased in the chicken. Therefore, these data suggest that NPY has a pivotal role on the water homeostasis in the chicken.