Nongenomic effects of aldosterone on Ca2+ in M-1 cortical collecting duct cells.
BACKGROUND
Aldosterone at physiological levels induces rapid (<5 min) increases in intracellular protein kinase C (PKC) activity and a rise in calcium and pH in mineralocorticoid hormone target epithelia, such as distal colon and sweat gland. The end targets of these rapid responses in epithelia are Na+/H+ exchange and K+ channels.


METHODS
The mouse cortical collecting duct (CCD) M-1 cell line was grown to confluency and loaded with Fura-2 for spectrofluorescence measurements of intracellular free calcium at 37 degrees C bathed in Krebs solution.


RESULTS
Aldosterone (1 nmol/L) produced a rapid, transient peak increase in [Ca2+]i in M-1 cells. This effect was abolished upon removal of extracellular Ca2+, but was unaffected by pretreatment with spironolactone (10 micromol/L) or actinomycin D (10 micromol/L). However, pretreatment with the specific PKC inhibitor chelerythrine chloride (1 micromol/L) prevented the aldosterone-induced rise in [Ca2+]i. Dexamethasone, at a concentration 10,000-fold higher than aldosterone (10 micromol/L), also produced a transient increase in [Ca2+]i, but this response was significantly smaller than that of aldosterone. In contrast, hydrocortisone had no effect on [Ca2+]i at either nmol/L or micromol/L concentrations. Both of the sex steroids, 17beta-estradiol (10 nmol/L) and progesterone (10 nmol/L), induced protein kinase C-dependent increases in [Ca2+]i.


CONCLUSIONS
Aldosterone and sex steroid hormones activate intracellular calcium signaling in CCD cells via a nongenomic PKC-dependent pathway, which may have important implications for renal transport.
Harvey
B J
BJ
Wellcome Trust Cellular Physiology Research Unit, Department of Physiology, University College, Cork, Ireland. harvey@ucc.ie
Higgins
M
M
D000450:Aldosterone / Q000502:physiology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D003609:Dactinomycin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016678:Genome; D007425:Intracellular Membranes / Q000378:metabolism; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012964:Sodium / Q000037:antagonists & inhibitors / Q000378:metabolism; D013148:Spironolactone / Q000494:pharmacology
D004791:Enzyme Inhibitors; D000451:Mineralocorticoid Receptor Antagonists; D019384:Nucleic Acid Synthesis Inhibitors; D003609:Dactinomycin; D013148:Spironolactone; D000450:Aldosterone; D010042:Ouabain; D012964:Sodium; D011493:Protein Kinase C; D002118:Calcium