Saito N, Grossmann R
Graduate School of Bioagricultural Sciences, Nagoya University, Japan.
Comp Biochem Physiol A Mol Integr Physiol. 1998 Nov;121(3):235-9. doi: 10.1016/s1095-6433(98)10123-x.
The neurohypophysial hormone, arginine vasotocin (AVT), plays an important role in the osmoregulation of birds. After a prolonged period of water deprivation, plasma osmolality and plasma concentration of AVT are elevated. In this study, the effects of short term dehydration were examined in laying hens by measuring plasma osmolality, plasma levels of potassium, sodium and AVT and hypothalamic concentrations of mRNA encoding AVT during 8 h of water deprivation. Plasma osmolality increased significantly after at 6 h of water deprivation. Plasma sodium levels, however, did not change. Plasma potassium concentrations gradually decreased during dehydration. Plasma AVT levels and hypothalamic AVT mRNA levels increased significantly after 8 h. The results of this study demonstrate that depriving chickens of water results first in an increase in plasma osmolality followed by increases in AVT levels in plasma and AVT mRNA levels in the hypothalamus. The data indicate that the synthesis of AVT in the magnocellular neurons in the hypothalamus is activated soon after the animals are deprived of water. This indicates that both de novo synthesized AVT as well as AVT stored in the neurohypophysis are available to meet the increasing demands for the hormone during osmotic stress.
神经垂体激素精氨酸血管加压素（AVT）在鸟类的渗透压调节中起重要作用。经过长时间的缺水后，血浆渗透压和AVT的血浆浓度会升高。在本研究中，通过在缺水8小时期间测量血浆渗透压、血浆中钾、钠和AVT的水平以及下丘脑编码AVT的mRNA浓度，研究了短期脱水对蛋鸡的影响。缺水6小时后，血浆渗透压显著升高。然而，血浆钠水平没有变化。脱水过程中血浆钾浓度逐渐降低。8小时后，血浆AVT水平和下丘脑AVT mRNA水平显著升高。本研究结果表明，剥夺鸡的水分首先导致血浆渗透压升高，随后血浆中AVT水平和下丘脑中AVT mRNA水平升高。数据表明，动物缺水后不久，下丘脑大细胞神经元中AVT的合成被激活。这表明，新合成的AVT以及储存在神经垂体中的AVT都可用于满足渗透压应激期间对该激素不断增加的需求。
