Aquaporin-9 is a protein that in humans is encoded by the AQP9gene.
The aquaporins/major intrinsic protein are a family of water-selective membrane channels. Aquaporin 9 has greater sequence similarity with AQP3 and AQP7 and they may be a subfamily. Aquaporin 9 allows passage of a wide variety of noncharged solutes. AQP9 stimulates urea transport and osmotic water permeability; there are contradicting reports about its role in providing glycerol permeability. Aquaporin 9 may also have some role in specialized leukocyte functions such as immunological response and bactericidal activity.
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Damiano AE, Zotta E, Ibarra C (2006). "Functional and molecular expression of AQP9 channel and UT-A transporter in normal and preeclamptic human placentas". Placenta. 27 (11–12): 1073–81. doi:10.1016/j.placenta.2005.11.014. PMID16480766.