Dietary Na + intake in healthy humans changes the urine extracellular vesicle prostasin abundance while the vesicle excretion rate, NCC, and ENaC are not altered

• Published in: American journal of physiology. Renal physiology Vol. 317; no. 6; p. F1612
• Main Authors: Zachar, Rikke, Jensen, Boye L, Svenningsen, Per
• Format: Journal Article
• Language: English
• Published: United States 01-12-2019
• Subjects: Adenosine Triphosphatases - urine; Adult; Albuminuria - urine; Creatinine - urine; Diet, Sodium-Restricted; Electrolytes - urine; Epithelial Sodium Channels - drug effects; Epithelial Sodium Channels - metabolism; Exosomes - metabolism; Extracellular Vesicles; Humans; Kidney - pathology; Male; Renin-Angiotensin System; Serine Endopeptidases - urine; Sodium, Dietary - pharmacology; Solute Carrier Family 12, Member 3 - drug effects; Solute Carrier Family 12, Member 3 - metabolism; Young Adult; sodium; sodium-chloride cotransporter; epithelial Na+ channel; exosomes; urinary extracellular vesicles
• ISSN: 1522-1466
• DOI: 10.1152/ajprenal.00258.2019

Low Na
intake activates aldosterone signaling, which increases renal Na
reabsorption through increased apical activity of the NaCl cotransporter (NCC) and the epithelial Na
channel (ENaC). Na
transporter proteins are excreted in urine as an integral part of cell-derived extracellular vesicles (uEVs). It was hypothesized that Na
transport protein levels in uEVs from healthy humans reflect their physiological regulation by aldosterone. Urine and plasma samples from 10 healthy men (median age: 22.8 yr) were collected after 5 days on a low-Na
(70 mmol/day) diet and 5 days on a high-Na
(250 mmol/day) diet. uEVs were isolated by ultracentrifugation and analyzed by Western blot analysis for EV markers (CD9, CD63, and ALIX), transport proteins (Na
-K
-ATPase α
-subunit, NCC, ENaC α- and γ-subunits, and aquaporin 2), and the ENaC-cleaving protease prostasin. Plasma renin and aldosterone concentrations increased during the low-Na
diet. uEV size and concentration were not different between diets by tunable resistive pulse sensing. EV markers ALIX and CD9 increased with the low-Na
diet, whereas CD63 and aquaporin 2 excretion were unchanged. Full-length ENaC γ-subunits were generally not detectable in uEVs, whereas ENaC α-subunits, NCC, and phosphorylated NCC were consistently detected but not changed by Na
intake. Prostasin increased with low Na
in uEVs. uEV excretion of transporters was not correlated with blood pressure, urinary Na
and K
excretion, plasma renin, or aldosterone. In conclusion, apical Na
transporter proteins and proteases were excreted in uEVs, and while the excretion rate and size of uEVs were not affected, EV markers and prostasin increased in response to the low-Na
diet.