Intestinal Mineralocorticoid Receptor Contributes to Epithelial Sodium Channel–Mediated Intestinal Sodium Absorption and Blood Pressure Regulation

Figures

• 

  Figure 1. The mRNA expression levels of the ENaC family, SGK1, and NHE3 in the kidneys and various intestinal portions. The mRNA expression of α‐, β‐, and γ‐ENaC (A), SGK1 (B), and NHE3 (C) in various intestinal parts and in the kidneys (D), as measured by quantitative polymerase chain reaction. Gene expression in each intestinal portion is normalized to that of control mouse duodenum. The number of animals per group is indicated in parentheses. Data are presented as mean±SEM. *P<0.05 vs control. ENaC indicates epithelial sodium channel; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout; NHE3, sodium–hydrogen exchanger 3; SGK1, serum/glucocorticoid regulated kinase 1.

• 

  Figure 2. The mRNA expression levels of ENaC family members and SGK1 in the distal colon and kidneys with a low‐salt diet. The mRNA expression of ENaC and SGK1 in the distal colon (A) and in the kidneys (B) with a standard diet and a low‐salt diet, as measured by quantitative polymerase chain reaction. Gene expression is normalized to that of 18S rRNA and is expressed relative to that in control mice on a standard diet. Data are presented as mean±SEM. n=7 per genotype and group. P<0.05 vs *control, †standard diet. ENaC indicates epithelial sodium channel; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout; SGK1, serum/glucocorticoid regulated kinase 1.

• 

  Figure 3. Changes in fecal and urinary sodium excretion and systolic blood pressure under each treatment. Urinary (A–C) and fecal (D–F) sodium excretion and systolic blood pressure (G–I) with a standard diet, a high‐salt diet, and DOCA/salt treatment. Data are presented as mean±SEM. *P<0.05 vs control. DOCA indicates deoxycorticosterone acetate; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout.

• 

  Figure 4. Changes in urinary sodium excretion and blood pressure under DOC+SPL treatment. Gray lines indicate the changes under DOCA/salt treatment, as shown in Figure 3C and 3I. Black lines indicate the changes under DOC+SPL treatment. Urinary sodium excretion (A and B) and systolic blood pressure (D and E) in control and IEC‐MR‐KO mice. C, Urinary sodium excretion in all groups at 12 weeks of age. F, Blood pressure in all groups at 13 weeks of age. Arrows indicate the start of spironolactone treatment. Data are presented as mean±SEM. P<0.05 vs *control (Cont), # DOCA/salt. DOC+SPL indicates deoxycorticosterone acetate/salt treatment plus spironolactone; DOCA, deoxycorticosterone acetate; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout.

• 

  Figure 5. The mRNA expression levels of ENaC family members and NHE3 in the distal colon under each treatment. The mRNA expression in the distal colon of α‐ENaC (A), β‐ENaC (B), γ‐ENaC (C), SGK1 (D), and NHE3 (E) with a standard diet, a high‐salt diet, DOCA/salt treatment, and DOC+SPL treatment, as measured by quantitative polymerase chain reaction. Gene expression is normalized to that of 18S rRNA and is expressed relative to that in control mice on a standard diet. Data are presented as mean±SEM. n=6 to 8 per genotype and group. P<0.05 vs *control, †standard diet, §high‐salt diet, # DOCA/salt. DOC+SPL indicates deoxycorticosterone acetate/salt treatment plus spironolactone; DOCA, deoxycorticosterone acetate; ENaC, epithelial sodium channel; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout; NHE3, sodium–hydrogen exchanger 3; SGK1, serum/glucocorticoid regulated kinase 1.

• 

  Figure 6. Protein expression levels of ENaC family and SGK1 in the distal colon. A, Representative immunoblot showing the protein expression of each gene. The arrowhead indicates the β‐ENaC band and the arrow indicates the broad bands centered around 70 kDa, which represent the active γ‐ENaC form. B, Quantification of β‐ and γ‐ENaC protein expression levels after analysis using ImageJ. Levels are normalized to those of β‐actin and expressed relative to that in control mice on a standard diet. Data are presented as mean±SEM. n=5 per genotype and group. P<0.05 vs *control, †standard diet, §high‐salt diet. DOCA indicates deoxycorticosterone acetate; ENaC, epithelial sodium channel; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout; SGK1, serum/glucocorticoid regulated kinase 1.

• 

  Figure 7. The mRNA expression levels of ENaC family members and NHE3 in the kidneys with each treatment. The mRNA expression in the kidneys of α‐ENaC (A), β‐ENaC (B), γ‐ENaC (C), and NHE3 (D) with a standard diet, a high‐salt diet, and DOCA/salt treatment, as measured by quantitative polymerase chain reaction. Gene expression was normalized to that of 18S rRNA and is expressed relative to that in control mice on a standard diet. Data are expressed as mean±SEM. n=6 to 8 per genotype and group. P<0.05 vs †standard diet, §high‐salt diet. DOCA indicates deoxycorticosterone acetate; ENaC, epithelial sodium channel; IEC‐MR‐KO, intestinal epithelial cell–specific mineralocorticoid receptor knockout; NHE3, sodium–hydrogen exchanger 3.