Aldosterone potentiates 1,25-dihydroxyvitamin D3 action in renal thick ascending limb via a nongenomic, ERK-dependent pathway

David W. Good, Thampi George, Bruns A. Watts

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

Recently, we demonstrated that aldosterone inhibits HCO3 - absorption in the rat medullary thick ascending limb (MTAL) via a nongenomic pathway blocked by inhibitors of extracellular signal-regulated kinase (ERK) activation. Here we examined the effects on the MTAL of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], which regulates cell functions through nongenomic mechanisms in nonrenal systems. Addition of 1 nM 1,25(OH)2D3 to the bath decreased HCO3- absorption by 24%, from 15.0 ± 0.3 to 11.4 ± 0.5 pmol·min-1·mm-1 (P < 0.001). This inhibition was maximal within 60 min and was eliminated by pretreatment with actinomycin D, cycloheximide, or inhibitors of protein kinase C. In MTAL bathed with 1 nM aldosterone [added 15-20 min before 1,25(OH)2D 3], the absolute (5.6 ± 0.3 vs. 3.6 ± 0.3 pmol·min-1·mm-1) and fractional (49 ± 2 vs. 24 ± 2%) decreases in HCO3- absorption induced by 1,25(OH)2D3 were significantly greater than those in the absence of aldosterone (P < 0.05). The effect of aldosterone to potentiate inhibition by 1,25(OH)2D3 was not affected by spironolactone but was eliminated by the MAPK kinase/ERK inhibitor U-0126. U-0126 did not affect inhibition of HCO3 - absorption by 1,25(OH)2D3 alone. Aldosterone induced rapid activation of ERK via a transcription-independent pathway. We conclude that 1) 1,25(OH)2D3 inhibits HCO3 - absorption in the MTAL via a genomic pathway involving protein kinase C, which may contribute to 1,25(OH)2D3-induced regulation of urinary net acid and/or Ca2+ excretion and 2) aldosterone potentiates inhibition by 1,25(OH)2D3 through an ERK-dependent, nongenomic pathway. These results identify a novel regulatory interaction whereby aldosterone acts via nongenomic mechanisms to enhance the genomic response to 1,25(OH)2D3. Aldosterone may influence a broad range of biological processes, including epithelial transport, by modifying the response of target tissues to 1,25(OH)2D 3 stimulation.

Original languageEnglish (US)
Pages (from-to)C1122-C1130
JournalAmerican Journal of Physiology - Cell Physiology
Volume285
Issue number5 54-5
DOIs
StatePublished - Nov 2003

Keywords

  • 1,25-dihydroxycholecalciferol
  • Acid-base transport
  • Bicarbonate absorption
  • Calcium homeostasis
  • Kidney

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

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