Aquaglyceroporins form homotetrameric transmembrane channels, with each monomer independently mediating glycerol and water transport across the plasma membrane along their osmotic gradient (PubMed:10564231, PubMed:30420639, PubMed:35054513, PubMed:9514918). AQP9 is the primary route for glycerol uptake in hepatocytes, supporting hepatic gluconeogenesis (By similarity). It exhibits broad specificity and may transport various small, non-charged solutes, including carbamides, polyols, purines, and pyrimidines (PubMed:10564231). AQP9 may also facilitate hepatic urea extrusion (PubMed:10564231, PubMed:9514918). Due to its permeability to lactate, AQP9 might participate in the astrocyte-to-neuron lactate shuttle, supplying neurons with energy (PubMed:10564231, PubMed:35054513). Additionally, AQP9 is permeable to arsenite, contributing to arsenic excretion by the liver and providing partial protection against arsenic toxicity (PubMed:10564231). It is also permeable to H2O2 in vivo (PubMed:26837049). Could also be permeable to ammonium (By similarity). {ECO:0000250|UniProtKB:P56627, ECO:0000250|UniProtKB:Q9JJJ3, ECO:0000269|PubMed:10564231, ECO:0000269|PubMed:26837049, ECO:0000269|PubMed:30420639, ECO:0000269|PubMed:35054513, ECO:0000269|PubMed:9514918}. This is the function of AQP9 (aquaporin 9, ENSG00000103569).