Optimized Renal Transporter Quantification by Using Aquaporin 1 and Aquaporin 2 as Anatomical Markers: Application in Characterizing the Ontogeny of Renal Transporters and Its Correlation with Hepatic Transporters in Paired Human Samples
Renal transporters, which are primarily located in the proximal tubules, play an important role in secretion and nephrotoxicity of drugs. The goal of this study was to characterize the age-dependent protein abundance of human renal transporters. A total of 43 human kidneys, 26 of which were paired with livers from the same donors, were obtained and classified into three age groups: children (< 12 years), adolescents (12 to < 18 years), and adults (> 18 years). Protein abundance of kidney-specific anatomical markers, aquaporins 1 and 2 (markers of proximal and distal/collecting tubules, respectively), and 17 transporters was quantified by LC-MS/MS proteomics. Six out of 43 kidney samples were identified as outliers (Grubbs’ test) that were significantly different from the others with relatively higher aquaporin 2 to aquaporin 1 ratio, indicating that these cortex samples were likely contaminated by medulla (representing distal/collecting tubules). No significant age-related changes (age > 1 year) were observed for renal transporter abundance, albeit OCT2 abundance was modestly higher (< 50%) in adolescents than that in adults. Higher protein-protein correlation between transporters was observed in the kidney but abundance of transporters between tissues was not correlated. The use of aquaporins 1 and 2 provides a method for identifying kidney cortex with significant contamination from medulla containing distal and collecting tubules. The abundance and protein-protein correlation data can be used in physiologically based pharmacokinetic (PBPK) modeling and simulation of renal drug disposition and clearance in pediatric populations.
KEY WORDSontogeny renal transporters liver kidney quantitative proteomics paired samples
We thank Matthew Karasu from University of Washington for technical assistance with LC-MS/MS sample preparation, and Wendy Wang, Chengpeng Bi, Jeffrey Johnston, and Neil Miller from Children’s Mercy Hospital for their contribution to the RNA-seq processing.
This study was supported by UWRAPT (University of Washington Research Affiliate Program on Transporters sponsored by Biogen, Genentech, Gilead, Takeda and Merck & Co., Inc). BP was supported by Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH grant (R01.HD081299). The National Institute of Child Health and Human Development Brain and Tissue Bank for Developmental Disorders at the University of Maryland is funded by NIH contract HHSN275200900011C, reference no. N01-HD-9-0011.
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