Na⁺ dependence of K⁺‐induced natriuresis, kaliuresis and Na⁺/Cl⁻ cotransporter dephosphorylation

Abstract

These data indicate that acute K(+) -induced kaliuresis is ENaC dependent. Maximal K(+) excretion rates are attenuated when ENaC is physiologically down-regulated or pharmacologically blocked. NCC is dephosphorylated following acute K(+) loading under all dietary Na(+) regimens. This leads to natriuresis, even in severely Na(+) -restricted animals.

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“…Another result of the current study is that rats treated with a high sodium diet have a decreased ability to excrete K + . This result is in accordance with Jensen et al, who provide experimental data showing that ENaC activity is a rate-limiting element for powerful K + excretion, hindering K + excretion during high Na + conditions [43].…”

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“…The difference between Na + excretion in the presence and absence of intraperitoneal (i.p.) benzamil injection (benzamil-induced natriuresis [BIN]) has been widely used as a reflection of the amount of Na + that is being reabsorbed via ENaC (20,21). K + , administered by gavage, stimulates BIN in both male NMRI and female (C57BL/6) mice (data summarized in Table 1).…”

“…The K + gavage contained 2% mass K + (512 mM) and Cl -. This maneuver is well described to increase plasma K + , reduce NCC phosphorylation, and induce natriuresis and kaliuresis acutely (12,20). The Na + gavage had the same osmolarity (512 mM) and Clconcentration as the K + gavage.…”

“…Urine samples collected during handling of the mice prior to gavage were used as baseline values. Urine samples were collected as spot urine, as previously described (20).…”

“…Its inhibition allows more Na + to pass to tubular segments further downstream where ENaC-mediated Na + reabsorption establishes the lumen negative potential driving K + secretion (12,16,17). However, pharmacologic inhibition of NCC is insufficient to enhance K + excretion, despite a marked increase in Na + delivery to the ASDN (18,19); this stands in marked contrast to a KCl load, which rapidly stimulates both natriuresis and marked kaliuresis (12,20).…”