title: A new role for aquaporin 7 in insulin secretion.
abstract: BACGROUNS/AIMS: Several insulinotropic agents were recently reported to cause β-cell swelling. The possible participation of AQP7 to water transport was investigated in AQP7(+/+) or AQP7(-/-) mice.
  
  
  METHODS
  Aquaporin expression, insulin secretion, cell swelling and electrical activity were investigated in pancreatic islets.
  
  
  RESULTS
  RT-PCR revealed the expression of AQP5 and AQP8 mRNA. Double immunofluorescent labeling indicated their presence in β-cells. Whilst basal insulin release from isolated pancreatic islets incubated at 2.8 mM D-glucose did not differ between AQP7(+/+) or AQP7(-/-) mice, the secretion of insulin evoked by the omission of 50 mM NaCl, the substitution of 50 mM NaCl by 100 mM glycerol or a rise in D-glucose concentration to 8.3 mM and 16.7 mM was severely impaired in the islets from AQP7(-/-) mice. Yet, exposure of β-cells to either the hypotonic medium or a rise in D-glucose concentration caused a similar degree of swelling and comparable pattern of electrical activity in cells from AQP7(+/+) and AQP7(-/-) mice. Both the cell swelling and change in membrane potential were only impaired in AQP7(-/-) cells when exposed to 50 mM glycerol.
  
  
  CONCLUSIONS
  It is proposed, therefore, that AQP7 may, directly or indirectly, play a role at a distal site in the exocytotic pathway.
authors.affiliation: Laboratory of Experimental Hormonology, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Karim
authors.initials: K
authors.lastname: Louchami
authors.forename: Len
authors.initials: L
authors.lastname: Best
authors.forename: Peter
authors.initials: P
authors.lastname: Brown
authors.forename: Myrna
authors.initials: M
authors.lastname: Virreira
authors.forename: Emeline
authors.initials: E
authors.lastname: Hupkens
authors.forename: Jason
authors.initials: J
authors.lastname: Perret
authors.forename: Olivier
authors.initials: O
authors.lastname: Devuyst
authors.forename: Shinichi
authors.initials: S
authors.lastname: Uchida
authors.forename: Christine
authors.initials: C
authors.lastname: Delporte
authors.forename: Willy J
authors.initials: WJ
authors.lastname: Malaisse
authors.forename: Renaud
authors.initials: R
authors.lastname: Beauwens
authors.forename: Abdullah
authors.initials: A
authors.lastname: Sener
mesh_terms: D000818:Animals; D051402:Aquaporin 5 / Q000235:genetics / Q000378:metabolism; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects; D005260:Female; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D012965:Sodium Chloride / Q000737:chemistry
chemical_list: C491927:Aqp7 protein, mouse; D051402:Aquaporin 5; D020346:Aquaporins; D007328:Insulin; C108330:aquaporin 8; D012965:Sodium Chloride; D005947:Glucose; D005990:Glycerol