Study of osmoregulation in birds

长期以来，人们对于渗透压感受器对渗透压调节的作用尚不清楚。最近，水通道蛋白4（AQP4）已成为渗透压感受器的候选者，但还没有明确的证据。我们克隆了鸡 AQP4 cDNA 并确定了其序列。我们分析了鸡下丘脑中与渗透刺激相关的AQP4基因表达。鸡体内的 AQP4 基因表达因高渗透压而增加。因此，这些结果表明 AQP4 可能涉及鸡的渗透压感受器。由于没有观察到哺乳动物中高渗透压会导致 AQP4 基因表达增加，因此这种增加是鸡中特有的现象。比较缺水后蛋鸡和肉鸡品系之间的精氨酸催产素 (AVT) 基因表达，两种品系的雏鸡体重均下降，血浆渗透压增加。在AVT基因表达方面，AVT基因表达在蛋鸡中增加，但在肉鸡中没有增加。这些结果表明两种菌株之间存在一些不同的渗透调节机制。神经肽Y（NPY）被认为在摄食行为中发挥着重要作用。但是，缺水后，鸡中的 NPY 基因表达增加。因此，这些数据表明 NPY 对鸡的水稳态具有关键作用。

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.