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Arachidonic Acid Activates Cation Channels in Bovine Adrenal Chromaffin Cells
Author(s) -
MochizukiOda Noriko,
Negishi Manabu,
Mori Kensaku,
Ito Seiji
Publication year - 1993
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1993.tb09830.x
Subject(s) - arachidonic acid , biophysics , chemistry , eicosapentaenoic acid , linoleic acid , biochemistry , patch clamp , fatty acid , oleic acid , endocrinology , medicine , biology , polyunsaturated fatty acid , enzyme , receptor
— Microscopic fluorescence analysis of fura‐2‐loaded bovine adrenal chromaffin cells demonstrates that ∼70% of the cells responded to arachidonic acid in increasing the intracellular Ca 2+ concentration. Because this increase was markedly less in the absence of external Ca 2+ , we examined the effect of arachidonic acid on Ca 2+ influx electrophysiologically. Bath application of 10 μ M arachidonic acid induced a long‐lasting inward current when the cell was clamped at ‐50 mV. Other fatty acids, such as oleic acid, linoleic acid, eicosatrienoic acid, and eicosa‐pentaenoic acid, were all ineffective. The current‐voltage relationships suggest that arachidonic acid may activate voltage‐insensitive channels. Arachidonic acid (2μ M ) activated a single‐channel current in the inside‐out patch, even in the presence of inhibitors of cyclooxygenase and lipoxygenase, possibly suggesting that arachidonic acid could activate channels directly. The onset delay of the inward channel current in the outside‐out patch configuration (54.02 ± 63.5 s; mean SD) was significantly shorter than that in the inside‐out patch one (197.3 ± 177.7 s). Washout of arachidonic acid decreased the probability of channel openings in the outside‐out patch but not in the inside‐out one. These results suggest that arachidonic acid activates channels reversibly from outside of the plasma membrane. The unitary conductarce for Ca 2+ of arachidonic acid‐activated channel was ∼17 pS. The arachidonic acid‐activated channel was permeable to Ba 2+ , Ca 2+ , and Na + but not to Cl − . The opening probability of the arachidonic acid‐activated channel did not depend on membrane potential. These results demonstrate that arachidonic acid activates cation‐selective, Ca 2+ ‐permeable channels in bovine adrenal chromaffin cells.