Abstract: TH-PO111
A GFR-Independent Method for Measuring Kidney Tubular Function
Session Information
- Pharmacology
October 24, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
- 2000 Pharmacology (PharmacoKinetics, -Dynamics, -Genomics)
Authors
- Karel, Isaac Z., The Ohio State University, Columbus, Ohio, United States
- Bajwa, Amandeep, The University of Tennessee Health Science Center, Memphis, Tennessee, United States
- Pabla, Navjot, The Ohio State University, Columbus, Ohio, United States
Background
Glomerular filtration rate (GFR) is the main functional index of kidney health and disease. Currently, no methods are available to directly measure tubular mass and function. Here we report a serendipitous finding that the in vitro cell viability dye resazurin, can be used in mice as an exogenous sensor of tubular function.
Methods
Mouse models of renal ischemia reperfusion, cisplatin nephrotoxicity, and rhabdomyolysis were used to assess the utility of resazurin as a sensor of tubular function and injury. Resazurin and its metabolites were measured in the blood and urine by fluorescence and mass spectrometry measurements.
Results
Intravenously injected resazurin exhibited significant plasma protein binding and was found to mainly undergo tubular secretion. Mechanistic studies showed that the blue-colored weakly fluorescent resazurin is taken up by tubular cells through the organic anion transporters, followed by conversion to highly fluorescent pink-colored resorufin by mitochondrial and cytosolic reductases, glucuronidation of resorufin to an orange-colored resorufin β-d-glucuronide, and subsequent efflux into the urine. We report a simple method where the intravenous injection of resazurin is followed by measurement of fluorescent metabolites in the urine provides a sensitive read-out of tubular function. In bilateral ischemia reperfusion, cisplatin nephrotoxicity, and rhabdomyolysis-associated AKI models, the resazurin-based method was able to sensitively detect loss of tubular function much earlier than the increase in serum creatinine levels. Strikingly, in mice with unilateral ischemia reperfusion injury, and genetic mutation-linked kidney hypoplasia, the resazurin-based method was able to detect loss of tubular mass and function despite normal GFR levels.
Conclusion
These findings establish the preclinical utility of resazurin as a rapid and sensitive exogenous marker of tubular function and support future examination in larger animals for potential clinical translation.
Funding
- NIDDK Support