title: Effects of acetaldehyde on hepatocyte glycerol uptake and cell size: implication of aquaporin 9.
abstract: BACKGROUND
  The effects of ethanol and acetaldehyde on uptake of glycerol and on cell size of hepatocytes and a role Aquaporin 9 (AQP9), a glycerol transport channel, were evaluated.
  
  
  METHODS
  The studies were done in primary rat and mouse hepatocytes. The uptake of [(14) C] glycerol was determined with hepatocytes in suspension. For determination of cell size, rat hepatocytes on coated dishes were incubated with a lipophilic fluorochrome that is incorporated into the cell membrane and examined by confocal microscopy. A three-dimensional z scan of the cell was performed, and the middle slice of the z scan was used for area measurements.
  
  
  RESULTS
  Acute exposure to acetaldehyde, but not to ethanol, causes a rapid increase in the uptake of glycerol and an increase in hepatocyte size, which was inhibited by HgCl(2) , an inhibitor of aquaporins. This was not observed in hepatocytes from AQP9 knockout mice, nor observed by direct application of acetaldehyde to AQP9 expressed in Xenopus Laevis oocytes. Prolonged 24-hour exposure to either acetaldehyde or ethanol did not result in an increase in glycerol uptake by rat hepatocytes. Acetaldehyde decreased AQP9 mRNA and AQP9 protein, while ethanol decreased AQP9 mRNA but not AQP9 protein. Ethanol, but not acetaldehyde, increased the activities of glycerol kinase and phosphoenolpyruvate carboxykinase.
  
  
  CONCLUSIONS
  The acute effects of acetaldehyde, while mediated by AQP9, are probably influenced by binding of acetaldehyde to hepatocyte membranes and changes in cell permeability. The effects of ethanol in enhancing glucose kinase, and phosphoenolpyruvate carboxykinase leading to increased formation of glycerol-3-phosphate most likely contribute to alcoholic fatty liver.
authors.affiliation: Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Potter
authors.forename: Ayman
authors.initials: A
authors.lastname: Koteish
authors.forename: James
authors.initials: J
authors.lastname: Hamilton
authors.forename: Xiaopu
authors.initials: X
authors.lastname: Liu
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.forename: Peter
authors.initials: P
authors.lastname: Agre
authors.forename: Esteban
authors.initials: E
authors.lastname: Mezey
mesh_terms: D000079:Acetaldehyde / Q000494:pharmacology*; D000818:Animals; D020346:Aquaporins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects*; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D005990:Glycerol / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D051381:Rats; D017207:Rats, Sprague-Dawley; D014982:Xenopus laevis
chemical_list: C491638:Aqp9 protein, mouse; D020346:Aquaporins; D000431:Ethanol; D000079:Acetaldehyde; D005990:Glycerol