Abstract
There is no simple method to measure glomerular filtration rate (GFR) in mice, which limits the use of mice in models of renal diseases. We aimed at simplifying the plasma clearance of iohexol in mice, using dried blood spot (DBS) sampling in order to reduce the amount of blood taken for analysis. GFR was measured simultaneously by a reference method in total blood—as described before—and tested method using DBS in fifteen male and six female C57BL/6J mice. Total blood extraction was 50 μL for the reference methods and 25μL for the tested methods, distributed in 5 samples. The agreement of GFR values between both methods was analyzed with the concordance correlation coefficient (CCC), total deviation index (TDI) and coverage probability (CP). The agreement between both methods was excellent, showing a TDI = 8.1%, which indicates that 90% of the GFR values obtained with DBS showed an error ranging from − 8 to + 8% of the reference method; a CCC of 0.996 (CI: 0.992), reflecting high precision and accuracy and a CP of 94 (CI: 83), indicating that 6% of the GFR values obtained with DBS had an error greater than 10% of the method in blood. So, both methods are interchangeable. DBS represent a major simplification of GFR measurement in mice. Also, DBS improves animal welfare by reducing the total blood required and refining the procedure.
Highlights
Mouse models are very useful to study the pathogenesis of renal diseases
The total deviation index (TDI) was 8.1%, which means that 90% of the glomerular filtration rate (GFR) values obtained with the tested method in dried blood spot (DBS) showed an error ranging from − 8 to + 8% when compared with the reference method in total blood
The coverage probability (CP) was 94, which indicates that only 6% of the GFR values obtained with DBS had an error range greater than 10% of the method in blood (Table 2)
Summary
Mouse models are very useful to study the pathogenesis of renal diseases. In these models, disease progression is generally evaluated by changes in renal histology and glomerular filtration rate (GFR). Our group developed a simple, reproducible and reliable method to measure GFR in conscious rodents by means of the plasma clearance iohexol[1,8]. Iohexol is measured by HPLC–UV and the iohexol plasma clearance determined as the ratio between the dose of iohexol and the area under the curve[8] This method offers several advantages such as the use of a non-radioactive contrast; mice are conscious and unrestricted which avoids unpredictable changes in GFR due to anesthesia; need of few samples and a total blood volume of 50 μL per procedure without vein catheterization. Our hypothesis is that DBS sampling is a more simple approach to the measurement of GFR in mice by iohexol clearance and will help in reducing even more the total blood required per test, a relevant aspect of animal care in research
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