Jouanin C
Laboratoire de Zoologie (Mammifères et oiseaux), Muséum national d'Histoire naturelle, 55, rue, de Buffon, F 75005 Paris.
Ann Pharm Fr. 2000 Oct;58(5):346-50.
Oceanic birds feed mainly on marine invertebrates which are isosmotic with sea water. The kidneys of birds have a low concentrating ability and are unable to produce urine with a sodium concentration more than 300mmol/l. How do these birds avoid dehydration? The excess salt is eliminated by the secretory work of a paired gland in the head known for centuries to anatomists as nasal glands or supraorbitary glands, and now that their function is elucidated called salt excreting glands or simply salt glands. They connect through a duct with the nasal cavity. Oceanic birds expel by the nares a clear and colourless watery liquid that contains primarily Na(+) and Cl(-), at high and constant concentration, with a small amount of K(+) and HCO(3)(-). These salt glands do not function continually as the kidney does, becoming active only in response to an osmotic load. The salt gland of oceanic birds is one of the most efficient systems of ionic transport in the living world.
海洋鸟类主要以与海水等渗的海洋无脊椎动物为食。鸟类的肾脏浓缩能力较低，无法产生钠浓度超过300mmol/l的尿液。这些鸟类是如何避免脱水的呢？多余的盐分通过头部一对腺体的分泌作用排出，解剖学家几个世纪以来都知道这个腺体，称之为鼻腺或眶上腺，现在由于其功能已被阐明，称为排盐腺或简称为盐腺。它们通过导管与鼻腔相连。海洋鸟类通过鼻孔排出一种清澈无色的水样液体，其主要含有高浓度且恒定的Na(+)和Cl(-)，还有少量的K(+)和HCO(3)(-)。这些盐腺不像肾脏那样持续发挥作用，仅在对渗透压负荷作出反应时才会变得活跃。海洋鸟类的盐腺是生物界最有效的离子运输系统之一。
