Direct fluorometric analysis of a newly synthesised fluorescein-labelled marker for glomerular filtration rate

Abstract

There is an obvious and growing medical need for an accurate determination of kidney function in the diagnosis and management of renal diseases. The glomerular filtration rate (GFR) is the accepted gold standard measurement of kidney function. Several approaches to estimate the GFR are available, but most of them are inconvenient and, therefore, of limited acceptance. A new method of quantification with fluorescein-isothiocyanate (FITC) sinistrin (FS), a novel GFR marker, has been evaluated. The method is based on the fluorescence label of FS and can be performed with a standard fluorometer. To control the interference of protein with the fluorescence signal, a calibration function was developed. The accuracy of the fluorometric method established is comparable to the so-called "gold standard" of enzymatic determination of polyfructosan. Moreover, FS is easy to handle and requires low-cost instruments. Our results demonstrate the potential of the direct fluorometric analysis of the new FITC-labelled marker of being a precise, simple, rapid and cost-effective method for diagnosing disturbed kidney function and monitoring its treatment efficacy. The dramatic decrease in analytical effort will result in a significantly higher acceptability of GFR determination.

Online feedback–controlled renal constant infusion clearances in rats

“…The distribution and excretion process of the renal marker FITC-S 14,[17][18][19] (FITC-labeled active pharmaceutical ingredient of the commercial GFR marker Inutest Fresenius Kabi, Linz, Austria) in a CIC experiment was simulated by using Matlab (Mathworks, Natick, MA). The time periods to achieve steady state with different combinations of loading doses and maintenance infusion rates at different GFR levels were simulated.…”

“…The feedback regulation system is based on the fluorescent renal marker fluorescein isothiocyanate-sinistrin (FITC-S) 14,[17][18][19] and its transcutaneous measurement in the interstitial fluid by a miniaturized device published recently. 15 The new technique allows the exact identification of the steadystate marker concentration and the monitoring of its maintenance in real time over the entire study period.…”

Transcutaneous assessment of renal function in conscious rats with a device for measuring FITC-sinistrin disappearance curves

“…Moreover, the fructan moiety of the FITC-sinistrin was determined enzymatically in plasma samples as a gold standard technique of GFR measurement, as published before. 7,16,17,19 From the plasma samples the rate constant and elimination half-life were calculated using an established one compartment model ( Figure 2b). 7,16,17 In addition, a two compartment model was fitted to the transcutaneous data for half-life determination (see Supplementary Data online).…”

Simplified Method to Measure Glomerular Filtration Rate by Iohexol Plasma Clearance in Conscious Rats

“…FITC-inulin or FITC-sinistrin have been used in both rats and mice as GFR markers [30,31,32]. Despite the fact that analytical procedures for determining the fluorescence of the compound offer adequate sensitivity, and are quick and easy to perform, the procedures necessitate minor surgery either for cannulation or for micro-osmotic pump implantation.…”