Abstract: SA-PO1068

Mineralocorticoids Modulate the Expression of the Beta-3 Subunit of the Na +, K + - ATPase in the Renal Collecting Duct

Session Information

Category: Hypertension

  • 1102 Hypertension: Basic and Experimental - Renal Causes and Consequences

Authors

  • Rojas, Macarena, Millennium Institute on Immunology and Immunotherapy, ICBM, Facultad de Medicina Universidad de Chile, Santiago, Chile
  • Leon, Pablo Andres, Universidad de Chile, Santiago, Chile
  • Barrientos, Victor Manuel, Millennium Institute on Immunology and Immunotherapy, ICBM, Facultad de Medicina Universidad de Chile, Santiago, Chile
  • Alzamora, Rodrigo, University of Chile, Santiago, Chile
  • Michea, Luis F., Millennium Institute on Immunology and Immunotherapy, ICBM, Facultad de Medicina Universidad de Chile, Santiago, Chile
Background

Renal sodium reabsorption depends on the activity of the Na+,K+-ATPase (NKA) a/b heterodimer. Four a (a1-4) and three b subunit isoforms (b1-3) had been described. It is accepted that renal tubule cells express a1/b1. Aldosterone stimulates NKA se activity and may modulate a1/b1 expression. However, some studies suggested the presence of β3 in the kidney. We hypothesized that the β3 isoform of the NKA is expressed by tubular cells of the distal nephron and is modulated by mineralocorticoids.

Methods

We studied kidney from rats (male SD) and mice (male C57BL/6). β3 mRNA distribution was determined by qRT-PCR and in situ hybridization (ISH). We compared the abundance of renal β3 mRNA to the abundance in other tissues known to express β3 mRNA (testis, lung, liver). β3 protein was analyzed by western blot. In addition, convoluted proximal tubules (CPT), cortical collecting ducts (CCD) and inner medullary collecting ducts (IMCD) were isolated for qRT-PCR studies. The MR-dependence of β3 expression was studied in adrenalectomized (ADX) rodents with or without MR replacement therapy (DOCA; 7.6 mg/100 g b.w.; 5 days). We also tested the effect of the pharmacological MR blockade (Sprinololactone, SPIRO, 25 mg/kg/day)

Results

Kidney tissue express β3 mRNA, with higher relative abundance in medulla (12.2±0.2- vs. 1.0±0.2 in cortex; n=3, p<0.05). ISH studies showed the preferential expression of β3 mRNA in collecting duct principal cells of cortex and medulla. IMCD presented 4-fold higher abundance of β3 mRNA as compared to CPT (n=4, p<0.05). ADX rodents showed increased β3 mRNA and protein abundance by 3-fold and 2-fold respectively (n=4, p<0.05). The increase of β3 was prevented by DOCA. SPIRO increased medullary β3 mRNA (4-fold) and protein (2-fold, n=4, p<0.05). No changes in the abundance of β1 (cortical/medullar) β3 (cortical) were detected after ADX or Spiro.

Conclusion

We show that the β3 isoform of the Na+,K+-ATPase is mainly expressed in collecting duct principal cells of renal under the modulation of mineralocorticoids.
FONDECYT 1130550, FONDECYT 1171869, FONDECYT 1151423; IMII P09-016-F

Funding

  • Government Support - Non-U.S.