title: Transcutaneous measurement of glomerular filtration rate using FITC-sinistrin in rats.
abstract: BACKGROUND
  Inulin/sinistrin (I/S) clearance is a gold standard for an accurate assessment of glomerular filtration rate (GFR). Here we describe and validate an approach for a transcutaneous determination of GFR by using fluorescein-isothiocyanate-labelled sinistrin (FITC-S) in rats.
  
  
  METHODS
  Using a small animal imager, fluorescence is measured over the depilated ear of a rat after the injection of FITC-S. The decay curve of fluorescence is used for the calculation of half-life and GFR. The thus obtained transcutaneous data were validated by simultaneously performed enzymatic and fluorometric measurements in plasma of both FITC-S and sinistrin.
  
  
  RESULTS
  The results of enzymatic sinistrin determination versus transcutaneous half-life of FITC-S or plasma fluorescence correlated well with each other (R(2) > 0.90). Furthermore, Bland-Altman analyses proved a good degree of agreement of the three methods used. The measurements performed in healthy animals as well as different models of renal failure demonstrate its appropriateness in a wide range of renal function.
  
  
  CONCLUSIONS
  The transcutaneous method described offers a precise assessment of GFR in small animals. As neither blood and/or urine sampling nor time-consuming lab work is required, GFR can be determined immediately after the clearance procedure is finished. This method, therefore, simplifies and fastens GFR determinations in small lab animals compared to conventional bolus clearance techniques based on blood sampling. A low-cost device for the measurement of transcutaneous fluorescence intensity over time is under construction.
authors.affiliation: InnovationLab GmbH, Speyerer Str. 4, D-69115 Heidelberg, Germany. daniel.schock-kusch@innovationlab.biz
authors.forename: Daniel
authors.initials: D
authors.lastname: Schock-Kusch
authors.forename: Maliha
authors.initials: M
authors.lastname: Sadick
authors.forename: Nadja
authors.initials: N
authors.lastname: Henninger
authors.forename: Bettina
authors.initials: B
authors.lastname: Kraenzlin
authors.forename: Guenter
authors.initials: G
authors.lastname: Claus
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Kloetzer
authors.forename: Christel
authors.initials: C
authors.lastname: Weiss
authors.forename: Johannes
authors.initials: J
authors.lastname: Pill
authors.forename: Norbert
authors.initials: N
authors.lastname: Gretz
mesh_terms: D000818:Animals; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D005919:Glomerular Filtration Rate; D007677:Kidney Function Tests / Q000379:methods; D008297:Male; D009844:Oligosaccharides; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D005456:Fluorescent Dyes; D009844:Oligosaccharides; D016650:Fluorescein-5-isothiocyanate; C064636:sinistrin