Abstract: TH-PO1025
Axial Heterogeneity of Phosphate-Dependent Glutaminase Expression and Response to Metabolic Acidosis
Session Information
- Acid Base: Basic
November 02, 2017 | Location: Hall H, Morial Convention Center
Abstract Time: 10:00 AM - 10:00 AM
Category: Fluid, Electrolytes, and Acid-Base
- 701 Acid-Base: Basic
Authors
- Lee, Hyun-Wook, University of Florida , Gainesville, Florida, United States
- Osis, Gunars, University of Florida , Gainesville, Florida, United States
- Harris, Autumn N, University of Florida , Gainesville, Florida, United States
- Fang, Lijuan, University of Florida , Gainesville, Florida, United States
- Verlander, Jill W., University of Florida , Gainesville, Florida, United States
- Weiner, I. David, University of Florida , Gainesville, Florida, United States
Background
Phosphate-dependent glutaminase (PDG) is critically important in renal ammoniagenesis and may also contribute to 2-oxoglutarate generation used for TCA-derived ATP generation. Although increased proximal tubule (PT) PDG expression during metabolic acidosis is well-recognized, its expression and regulation in other renal tubule cells is not well-characterized. This study’s purpose was to determine PDG's cellular expression in the kidney and the cell-specific response to metabolic acidosis.
Methods
C57Bl/6 mice were fed normal diet or were acid-loaded by adding HCl to chow for 7 days. Three separate PDG antibodies were used; all gave similar results.
Results
Under basal conditions, immunohistochemistry (IHC) showed PDG immunolabel throughout the renal nephron, collecting duct and papillary surface epithelium. Immunogold electron microscopy confirmed mitochondrial localization; gold label density was generally greater in mitochondria in distal tubule and collecting duct cells than in PT cells. The cellular distribution of PDG expression was verified using double-immunolabel IHC with NHE3, AQP1, NKCC2, and H+-ATPase. Cells with strong PDG expression were present in the proximal convoluted tubule, proximal straight tubule, descending and ascending thin limbs, thick ascending limb, distal convoluted tubule, connecting segment, and throughout the collecting duct. In the PT, label intensity was heterogeneous, with interspersed intensely- and weakly-labeled cells. In medullary collecting ducts, intercalated cells had greater expression than principal cells. In addition, intercalated cell expression was heterogeneous in CCD and CNT. Acid-loading increased the number of strongly PDG-positive PT cells, did not alter expression in cortical and medullary thick ascending limb (mTAL) in the OSOM or the entire collecting duct and decreased expression in mTAL in the ISOM.
Conclusion
(1) The finding of cellular heterogeneity in PT PDG expression, with acid-loading increasing the number of PT cells with intense PDG expression, identifies a new ammoniagenic regulatory mechanism. (2) The wide-spread expression of PDG in non-PT cells, which was not altered by acidosis, suggests PDG may contribute to glutamine-derived ATP generation via the TCA cycle.
Funding
- NIDDK Support