title: Quantification of osmotic water transport in vivo using fluorescent albumin.
abstract: Osmotic water transport across the peritoneal membrane is applied during peritoneal dialysis to remove the excess water accumulated in patients with end-stage renal disease. The discovery of aquaporin water channels and the generation of transgenic animals have stressed the need for novel and accurate methods to unravel molecular mechanisms of water permeability in vivo. Here, we describe the use of fluorescently labeled albumin as a reliable indicator of osmotic water transport across the peritoneal membrane in a well-established mouse model of peritoneal dialysis. After detailed evaluation of intraperitoneal tracer mass kinetics, the technique was validated against direct volumetry, considered as the gold standard. The pH-insensitive dye Alexa Fluor 555-albumin was applied to quantify osmotic water transport across the mouse peritoneal membrane resulting from modulating dialysate osmolality and genetic silencing of the water channel aquaporin-1 (AQP1). Quantification of osmotic water transport using Alexa Fluor 555-albumin closely correlated with direct volumetry and with estimations based on radioiodinated ((125)I) serum albumin (RISA). The low intraperitoneal pressure probably accounts for the negligible disappearance of the tracer from the peritoneal cavity in this model. Taken together, these data demonstrate the appropriateness of pH-insensitive Alexa Fluor 555-albumin as a practical and reliable intraperitoneal volume tracer to quantify osmotic water transport in vivo.
authors.affiliation: Division and Laboratory of Nephrology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain Medical School, Brussels, Belgium; johann.morelle@uclouvain.be.
authors.forename: Johann
authors.initials: J
authors.lastname: Morelle
authors.affiliation: Division and Laboratory of Nephrology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain Medical School, Brussels, Belgium;
authors.forename: Amadou
authors.initials: A
authors.lastname: Sow
authors.affiliation: de Duve Institute, Université Catholique de Louvain Medical School, Brussels, Belgium;
authors.forename: Didier
authors.initials: D
authors.lastname: Vertommen
authors.affiliation: Department of Nuclear Medicine, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain Medical School, Brussels, Belgium;
authors.forename: François
authors.initials: F
authors.lastname: Jamar
authors.affiliation: Department of Nephrology, University Hospital of Lund, Lund, Sweden; and.
authors.forename: Bengt
authors.initials: B
authors.lastname: Rippe
authors.affiliation: Division and Laboratory of Nephrology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain Medical School, Brussels, Belgium; Institute of Physiology, Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Devuyst
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000378:metabolism*; D001692:Biological Transport; D005452:Fluoresceins; D008297:Male; D051379:Mice; D009995:Osmosis; D010530:Peritoneal Dialysis / Q000379:methods*; D010537:Peritoneum / Q000378:metabolism; D012710:Serum Albumin, Bovine; D014867:Water / Q000378:metabolism*
chemical_list: D005452:Fluoresceins; D014867:Water; D051398:Aquaporin 1; D012710:Serum Albumin, Bovine
keywords: Alexa Fluor; aquaporin-1; intraperitoneal volume; osmosis; ultrafiltration