title: Expression of aquaporin-3 in human peritoneal mesothelial cells and its up-regulation by glucose in vitro.
abstract: BACKGROUND
  Aquaporin-3 (AQP3) is a member of the water channel family that is selective for the passage of not only water, but also glycerol and urea. Our recent study demonstrated the presence of aquaporin-1 in human peritoneal mesothelial cells (HPMC). Although transcripts encoding for AQP3 has been detected by reverse transcription-polymerase chain reaction (RT-PCR) in murine peritoneal mesothelium, to date there is no documentation of protein expression on peritoneal mesothelial cells.
  
  
  METHODS
  Our present study was designed to explore the gene and protein expression of AQP3 in HPMC and its regulation under different concentrations of glucose.
  
  
  RESULTS
  AQP3 protein was detected in the human peritoneal tissue by immunohistological staining using specific, affinity-purified polyclonal anti-AQP3 antibodies. AQ3 transcripts and protein expression in cultured HPMC were investigated by RT-PCR and immunoblotting analysis respectively. Cell permeability to glycerol (flux) was measured using [(14)C]glycerol incorporation. AQP3 transcript and protein were weakly expressed in HPMC constitutively. The gene expression of AQP3 and its protein biosynthesis in HPMC were inducible following exposure to glucose in a dose- and time-dependent manner (P < 0.0001). Glucose at a concentration of 200 mmol induced glycerol flux by 4.82-fold above the control value (P < 0.0001) and its effect was significantly inhibited by mercuric chloride (P < 0.01).
  
  
  CONCLUSIONS
  Our novel observation demonstrated the AQP3 expression and biosynthesis in HPMC and in vitro studies revealed that glycerol permeability in HPMC was up-regulated by glucose. Further study is warranted to elucidate the role of AQP3 in HPMC for maintaining the ultrafiltration of the peritoneal membrane.
authors.affiliation: Division of Nephrology, Department of Medicine, University of Hong Kong, Room 409 Professorial Block, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong, People's Republic of China. knlai@hkucc.hku.hk
authors.forename: Kar Neng
authors.initials: KN
authors.lastname: Lai
authors.forename: Joseph C K
authors.initials: JC
authors.lastname: Leung
authors.forename: Loretta Y Y
authors.initials: LY
authors.lastname: Chan
authors.forename: Sydney
authors.initials: S
authors.lastname: Tang
authors.forename: Fu Keung
authors.initials: FK
authors.lastname: Li
authors.forename: Sing Leung
authors.initials: SL
authors.lastname: Lui
authors.forename: Tak Mao
authors.initials: TM
authors.lastname: Chan
mesh_terms: D051400:Aquaporin 3; D020346:Aquaporins / Q000032:analysis / Q000235:genetics*; D002250:Carbon Radioisotopes; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D004234:Diuretics, Osmotic / Q000494:pharmacology; D004847:Epithelial Cells / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D005990:Glycerol / Q000493:pharmacokinetics; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D008353:Mannitol / Q000494:pharmacology; D010537:Peritoneum / Q000166:cytology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: C496027:AQP3 protein, human; D020346:Aquaporins; D002250:Carbon Radioisotopes; D004234:Diuretics, Osmotic; D051400:Aquaporin 3; D008353:Mannitol; D005947:Glucose; D005990:Glycerol