An oxidized metabolite of linoleic acid increases intracellular calcium in rat adrenal glomerulosa cells.
EKODE, an epoxy-keto derivative of linoleic acid, was previously shown to stimulate aldosterone secretion in rat adrenal glomerulosa cells. In the present study, we investigated the effect of exogenous EKODE on cytosolic [Ca(2+)] increase and aimed to elucidate the mechanism involved in this process. Through the use of the fluorescent Ca(2+)-sensitive dye Fluo-4, EKODE was shown to rapidly increase intracellular [Ca(2+)] ([Ca(2+)](i)) along a bell-shaped dose-response relationship with a maximum peak at 5 microM. Experiments performed in the presence or absence of Ca(2+) revealed that this increase in [Ca(2+)](i) originated exclusively from intracellular pools. EKODE-induced [Ca(2+)](i) increase was blunted by prior application of angiotensin II, Xestospongin C, and cyclopiazonic acid, indicating that inositol trisphosphate (InsP(3))-sensitive Ca(2+) stores can be mobilized by EKODE despite the absence of InsP(3) production. Accordingly, EKODE response was not sensitive to the phospholipase C inhibitor U-73122. EKODE mobilized a Ca(2+) store included in the thapsigargin (TG)-sensitive stores, although the interaction between EKODE and TG appears complex, since EKODE added at the plateau response of TG induced a rapid drop in [Ca(2+)](i). 9-oxo-octadecadienoic acid, another oxidized derivative of linoleic acid, also increases [Ca(2+)](i), with a dose-response curve similar to EKODE. However, arachidonic and linoleic acids at 10 microM failed to increase [Ca(2+)](i) but did reduce the amplitude of the response to EKODE. It is concluded that EKODE mobilizes Ca(2+) from an InsP(3)-sensitive store and that this [Ca(2+)](i) increase is responsible for aldosterone secretion by glomerulosa cells. Similar bell-shaped dose-response curves for aldosterone and [Ca(2+)](i) increases reinforce this hypothesis.
Payet
Marcel D
MD
Department of Physiology, University of Sherbrooke, QC, Canada J1H 5N4. marcel.payet@usherbrooke.ca
Goodfriend
Theodore L
TL
Bilodeau
Lyne
L
Mackendale
Cherilu
C
Chouinard
Lucie
L
Gallo-Payet
Nicole
N
D000450:Aldosterone / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000378:metabolism; D066298:In Vitro Techniques; D007293:Inosine Triphosphate / Q000096:biosynthesis; D019787:Linoleic Acid / Q000378:metabolism / Q000494:pharmacology*; D009829:Oleic Acids / Q000378:metabolism / Q000494:pharmacology*; D010084:Oxidation-Reduction; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013256:Steroids / Q000096:biosynthesis; D015384:Zona Glomerulosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
C474654:12,13-epoxy-9- keto-10-octadecenoic acid; D005227:Fatty Acids; D009829:Oleic Acids; D013256:Steroids; D000804:Angiotensin II; D007293:Inosine Triphosphate; D000450:Aldosterone; D019787:Linoleic Acid; D000242:Cyclic AMP; D000252:Calcium-Transporting ATPases; D002118:Calcium