Kidney Week

Abstract: SA-PO1068

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

Session Information

• Hypertension: Basic and Experimental - Treatment and Mechanisms
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

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

Macarena Rojas,

• Leon, Pablo Andres, Universidad de Chile, Santiago, Chile

Pablo Andres Leon,

• Barrientos, Victor Manuel, Millennium Institute on Immunology and Immunotherapy, ICBM, Facultad de Medicina Universidad de Chile, Santiago, Chile

Victor Manuel Barrientos,

• Alzamora, Rodrigo, University of Chile, Santiago, Chile

Rodrigo Alzamora,

• Michea, Luis F., Millennium Institute on Immunology and Immunotherapy, ICBM, Facultad de Medicina Universidad de Chile, Santiago, Chile

Luis F. Michea,

Background

Renal sodium reabsorption depends on the activity of the Na⁺,K⁺-ATPase (NKA) a/b heterodimer. Four a (a_1-4) and three b subunit isoforms (b_1-3) 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.