A Ras-dependent chloride current activated by adrenocorticotropin in rat adrenal zona glomerulosa cells.
In the present study, we report that ACTH induces a transient chloride current. The lack of correlation between ACTH-induced cAMP production and amplitude of the Cl- current, as well as the absence of stimulation by forskolin or 8Br-cAMP indicated that the ACTH-induced current was not cAMP-dependent. We explored the possibility that one or several elements of the Ras/Raf MAPK cascade were involved. Indeed, we found that ACTH at 10(-10) M induced activation of Ras. Inhibition of the current by QEHA peptide, a Gbetagamma sequestrant, demonstrated that Gbetagamma subunits transduced the message. Blockage of the Ras activation using an inhibitor of farnesyl transferase (BZA-5B) or the monoclonal antibody H-Ras(259) abrogated the current. Moreover, the addition of Ras-GTPyS in the pipette medium gave rise to the Cl- current. Treatment of the cells with BZA decreased the aldosterone secretion induced by 10(-10) M ACTH but not that induced by 10(-8) M ACTH, confirming the involvement of Ras in steroid secretion. We conclude that ACTH triggers a Cl- current through the activation of the Ras protein by Gbetagamma subunits. This current, activated at physiological ACTH concentrations (1 to 100 pM) where cAMP production is very low, could play a significant role in aldosterone production.
Chorvátová
A
A
Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, Québec, Canada.
Gendron
L
L
Bilodeau
L
L
Gallo-Payet
N
N
Payet
M D
MD
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000450:Aldosterone / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007700:Kinetics; D009842:Oligopeptides / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D015384:Zona Glomerulosa / Q000166:cytology / Q000502:physiology*
D018118:Chloride Channels; D009842:Oligopeptides; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000450:Aldosterone; D000324:Adrenocorticotropic Hormone; D000242:Cyclic AMP; D016283:Proto-Oncogene Proteins p21(ras)