ATP receptor-mediated increase of Ca ionophore-stimulated arachidonic acid release from PC12 pheochromocytoma cells.
Phospholipase A2 has recently been proposed as the effector enzyme involved in the receptor-mediated release of arachidonic acid (AA). Released AA and its metabolites have been demonstrated to play an important role in the regulation of cell functions. [3H]AA release from prelabeled PC12 cells was stimulated by a Ca ionophore such as ionomycin or A23187. Although ATP and its effective analog, adenosine 5'-O-(3-thiotrisphosphate) (ATP gamma S), 2-methylthio ATP and 3'-O-(4-benzoyl)benzoyl ATP, did not stimulate [3H]AA release on their own, they did enhance Ca ionophore-stimulated [3H]AA release. The effect of ATP analogs was dose-dependent. ADP, UTP, GTP, ITP, alpha beta-methylene ATP, beta gamma-methylene ATP and 8-bromo ATP showed no effect or very limited effect. The effect of ATP gamma S was antagonized by suramin, a putative P2Y receptor antagonist. The effective ATP analogs also increased [Ca2+]i (cytosolic free Ca2+ concentration) via Ca2+ influx. However, the addition of 50 mM KCl or 10 microM bradykinin, which are well-known to increase [Ca2+]i by different pathways, did not stimulate [3H]AA release, either with or without the Ca ionophore. The addition of phorbol 12-myristate 13-acetate, an activator of protein kinase C, showed no effect on [3H]AA release, either with or without the Ca ionophore. These data suggest that 1) ATP increased Ca ionophore-stimulated AA release via a P2Y-like ATP receptor, and that 2) the elevation of [Ca2+]i by ATP does not quantitatively explain the ATP-stimulated AA release in PC12 cells.
Murayama
T
T
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Oda
H
H
Watanabe
A
A
Nomura
Y
Y
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D016257:Fura-2; D015759:Ionomycin / Q000494:pharmacology; D016716:PC12 Cells; D010673:Pheochromocytoma / Q000378:metabolism*; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000187:drug effects*
D018048:Receptors, Purinergic P2; D016718:Arachidonic Acid; D015759:Ionomycin; D000255:Adenosine Triphosphate; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2