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Kidney Week

Abstract: FR-PO516

Role of Paraoxonase 3 (PON3) in Regulating Epithelial Sodium Channel (ENaC)-Mediated Na+ Transport in Distal Nephron

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1101 Fluid, Electrolyte, and Acid-Base Disorders: Basic

Authors

  • Shi, Shujie, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Mutchler, Stephanie, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Whelan, Sarah Christine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Marciszyn, Allison L., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Kleyman, Thomas R., University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
Background

PON3 is expressed in the aldosterone-sensitive distal nephron, where ENaC plays an essential role in maintaining Na+/ K+ homeostasis in the kidney. The aims of our study were to determine the physiological roles of PON3 in renal Na+ and K+ handling. We hypothesize that PON3 functions as a molecular chaperone to regulate ENaC expressionand Na+ reabsorption in the kidney.

Methods

We have obtained a Pon3 global knockout mouse model and examined the effect of PON3 on ENaC functional expression using several approaches, including biochemistry, immunohistochemistry, electrophysiology, and whole animal metabolic cage studies.

Results

Pon3 KO mice have normal kidney histology without evidence of inflammation or injury. At baseline, Pon3 KO mice have a significantly lower blood [K+] and higher blood [Na+] when compared to WT littermates. Amiloride-induced natriuresis was significantly greater in the KO mice, reflecting, in part, an upregulation in ENaC-dependent Na+reabsorption in the absence of the PON3. Immunoblotting of whole kidney lysates indicated that the total abundance of ENaC subunits was not altered in KO mice. However, γENaC was more apically distributed within the cortical collecting ducts (CCD) of the KO kidneys. Single channel recordings of ENaC in split-open tubules freshly isolated from WT or Pon3 KO mice kidneys demonstrated that open probability (PO) was similar between the two groups of animals. However, the number of active channels per patch (N) was significantly higher in the KO kidneys, resulting in a higher ENaC activity (NPO) in the distal nephron segments of Pon3 KO mice. Consistent this notion, we found that γENaC surface abundance was increased in mCCD cells when PON3 expression was knocked down by siRNA.

Conclusion

Together, our data suggest that Pon3 KO mice have upregulated Na+ reabsorption and K+ secretion, likely a result of increased ENaC functional expression in the absence of PON3.

Funding

  • NIDDK Support