Role of de novo protein synthesis and calmodulin in rapid activation of Na(+)-H+ exchange of aldosterone in frog diluting segment.
1. In the amphibian early distal tubule aldosterone activates the Na(+)-H+ exchangers, resulting in an increase in intracellular pH (pHi). Since this activation is rapid (within 30 min), it may be mediated by either a genomic or non-genomic pathway. 2. pHi was measured in single microperfused early distal tubule segments using the fluorescent probe 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF). 3. A 30 min incubation in aldosterone increased both resting pHi and the setpoint of the Na(+-H+ exchanger. These changes were prevented by the mineralocorticoid receptor antagonist, spironolactone. 4. Actinomycin D and cycloheximide, inhibitors of transcription and translation, respectively, were without effect on resting pHi, but inhibited activation of the Na(+)-H+ exchanger by aldosterone. 5. The effect of aldosterone upon pHi and setpoint was also prevented by the calcium-calmodulin antagonist, W-7. 6. These results indicate that, although the response to aldosterone is rapid, aldosterone binds to a specific mineralocorticoid receptor which then triggers gene activation followed by de novo protein synthesis. Furthermore, since calmodulin is a known activator of the Na(+)-H+ exchanger, and the response is inhibited by W-7, it is suggested that this protein may be calmodulin.
Cooper
G J
GJ
Department of Physiology, University of Leeds, UK.
Hunter
M
M
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001711:Biotransformation / Q000187:drug effects; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007686:Kidney Tubules, Distal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011896:Rana temporaria; D018161:Receptors, Mineralocorticoid / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013148:Spironolactone / Q000494:pharmacology
D002147:Calmodulin; D000451:Mineralocorticoid Receptor Antagonists; D011500:Protein Synthesis Inhibitors; D018161:Receptors, Mineralocorticoid; D017923:Sodium-Hydrogen Exchangers; D013148:Spironolactone; D000450:Aldosterone