全世界每年有許多肝病和腎病患者因血液中氨含量過多而中毒死亡，對此,，美國和日本科學(xué)家表示,，他們已尋找到可降低患者血液中氨含量的方法。
在4月份出版的《FASEB》雜志上,，科學(xué)家介紹說,，河豚魚體內(nèi)的一種蛋白能將氨從其腮中排出體外,，這種蛋白同人體Rh血蛋白極其類似,，因此通過對Rh血蛋白的研究，有望開發(fā)出幫助患者排出體內(nèi)有害氨的新方法,。
對肝病和腎病患者而言,，及時有效地排除體內(nèi)自然產(chǎn)生的氨十分重要,。人類因?yàn)榇竽X十分容易受到氨的影響，低含量氨能夠?qū)е禄颊叱霈F(xiàn)輕微或嚴(yán)重的思緒混亂,、睡意或顫栗,，而高含量氨則導(dǎo)致他們昏迷并最終死亡。人體中的Rh血蛋白通常用于幫助人們決定血型,，例如具有A,、B、AB或O陽性血型的人,，其體內(nèi)紅血細(xì)胞表面有Rh血蛋白,，而具有A、B,、AB或O陰性血型的人,，其體內(nèi)紅血細(xì)胞表面則沒有Rh血蛋白。
科學(xué)家表示,，Rh血蛋白將是今后醫(yī)治肝病患者體內(nèi)自然產(chǎn)生的高氨含量的方向,。在研究報告中，科學(xué)家介紹了河豚利用類似人體Rh血蛋白的蛋白將氨排出其體外的微觀過程,。據(jù)悉,，他們的發(fā)現(xiàn)與Rh血蛋白存在于許多有機(jī)物的事實(shí)結(jié)合起來，還有助于揭開進(jìn)化論之謎,。因?yàn)樗砻?，Rh血蛋白出現(xiàn)在動物系統(tǒng)進(jìn)化的早期，并一直在排出體內(nèi)氨方面起著十分重要的作用,。
部分英文原文：
The FASEB Journal. 2007;21:1067-1074.
Ammonia secretion from fish gill depends on a set of Rh glycoproteins
Tsutomu Nakada*, Connie M. Westhoff,, Akira Kato* and Shigehisa Hirose*,1
* Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan;
Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA; and
American Red Cross, Philadelphia, Pennsylvania, USA
1Correspondence: Department of Biological Sciences, Tokyo Institute of Technology, 4259-B-19 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan. E-mail: [email protected]
Ammonia excretion from the gill in teleost fish is essential for nitrogen elimination. Although numerous physiological studies have measured ammonia excretion, the mechanism of ammonia movement through the membranes of gill epithelial cells is still unknown. Mammalian Rh glycoproteins are members of a family of proteins that mediate ammonia transport in bacteria, yeast, and plants. We identified the Rh glycoprotein homologs, fRhag, fRhbg, fRhcg1, and fRhcg2, of the pufferfish, Takifugu rubripes. Northern blot, in situ hybridization, and immunohistochemistry revealed that the pufferfish erythroid Rh glycoprotein homologue fRhag was present in red blood cells and the hematological organs (spleen and kidney) in fish. All four pufferfish Rh glycoproteins are specifically localized in the gill and line the pillar cells, pavement cells, and the mitochondrion-rich cells. Heterologous expression in Xenopus oocytes showed that they mediate methylammonium (an analog of ammonium) transport. These results suggest that pufferfish Rh glycoproteins are involved in ammonia excretion from the gill. These findings challenge the classic view that ammonia excretion in the fish gill occurs by passive diffusion.—Nakada, T., Westhoff, C. M., Kato, A., Hirose, S. Ammonia secretion from fish gill depends on a set of Rh glycoproteins.
Key Words: RhAG • Rhesus glycoprotein • ammonium transporter • mitochondria-rich cell • teleost
