Abstract
The sensitivity of different renal regions to xenobiotics requires the development of a multiplex immunoassay for the simultaneous analysis of kidney biomarkers. Calbindin D28K is a distal tubule-specific protein that can be detected in urine under pathological conditions. In this study, a pair of anti-calbindin D28K antibodies was used in an immunoassay for the detection of calbindin D28K expression in rat and human kidney and urine. Comparative analysis of the immunoassay was performed on the Meso Scale Development (MSD) and Luminex platforms. Analysis on both platforms detected calbindin D28K concentrations between 100 ng/mL and 100 pg/mL. Luminex detected 10-fold the amount of calbindin D28K in samples analyzed as compared to MSD, whereas calbindin D28K level in rat and human urine was below detection limit in both platforms. The application of the immunoassays described herein may be useful in toxicological and pathological studies of distal tubular damage in rats and human.
Highlights
The high renal blood flow, renal biotransformation of chemicals to reactive metabolites, and the nephrons ability to concentrate tubular fluid render the kidney sensitive to xenobiotics
Urinary analysis of patients treated with Cisplatin as well as patients treated by extracorporeal shock wave lithotripsy has indicated that the expression of calbindin D28K can be increased under pathological conditions [5, 6]
The software used in Meso Scale Development (MSD) analysis regarded the lowest concentration (25 pg/mL) on standard curve to be below detection range
Summary
The high renal blood flow, renal biotransformation of chemicals to reactive metabolites, and the nephrons ability to concentrate tubular fluid render the kidney sensitive to xenobiotics. Due to the kidneys regional sensitivity to xenobiotics, it is important to colocalize sites of biomarkers release with pathological lesions [1]. Calbindin D28K is an intracellular, vitamin D-dependent, calcium-binding protein that is expressed in the epithelial cells of renal distal tubules [2, 3]. Previous studies have demonstrated the inhibitory effect of nephro-toxicants such as Cyclosporin A on the expression of calbindin D28K in distal tubules [4]. The specific localization of calbindin D28K in distal tubules along with its pathophysiological release in urine makes this protein a potential biomarker for distal tubule damage
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