Cytochrome P450 products and arachidonic acid-induced, non-store-operated, Ca2+ entry in cultured bovine endothelial cells

Endothelial cells possess multiple mechanisms for the control of Ca2+ influx during agonist and mechanical stimulation. Increased intracellular Ca2+ during such events is important in the production of vasoactive substances including NO, prostacyclin, and, possibly, endothelium-derived hyperpolarizing factor(s). The present studies examined the effect of arachidonic acid on cellular Ca2+ entry and the underlying mechanisms by which this fatty acid regulates entry. Studies were conducted in cultured bovine aortic endothelial cells (passages 3 to 6) with changes in intracellular Ca2+ determined using the fluorescent Ca2+-sensitive indicator fura 2. Arachidonic acid (1 to 50 mu M) stimulated Ca2+ entry from the superfusate without affecting Ca2+ release from intracellular stores. 2-aminoethoxydiphenyl borate (2APB) (100 mu M) added at the peak of Ca2+ entry did not inhibit arachidonic acid-induced Ca2+ entry but, in contrast, significantly inhibited entry stimulated by ATP (1 mu M). Arachidonic acid-induced Ca2+ entry was inhibited by econazole (1 mu M), but not indomethacin (10 mu M) or nordihydroguairetic acid (10 mu M), suggesting the involvement of cytochrome P450 monooxygenase metabolite of arachidonic acid. Oleic acid (10 mu M) was ineffective in inducing Ca2+ entry, whereas linoleic acid (10 mu M) stimulated Ca2+ entry but by a mechanism insensitive to econazole. Collectively the data demonstrate that primary cultured aortic endothelial cells possess a Ca2+ entry mechanism modulated by arachidonic acid. This mode of Ca2+ entry appears to operate independently of store depletion-mediated mechanisms.