Bradykinin stimulates phospholipase D in PC12 cells by a mechanism which is independent of increases in intracellular Ca2+.
These experiments were designed to learn the role of bradykinin induced changes in intracellular Ca2+ in the activation of phospholipase D activity in PC12 cells. Ionomycin at a concentration of 0.1 microM caused an increase in intracellular Ca2+ comparable to bradykinin, but had no effect on phospholipase D activity. Carbachol, ATP, and thapsigargin also increased intracellular Ca2+ but had no effect on phospholipase D activity. Increases in intracellular Ca2+ may be a necessary but not a sufficient factor in the activation of phospholipase D. To investigate this issue, the bradykinin induced increase in intracellular Ca2+ was blocked by preincubating the cells in Ca(2+)-free media plus EGTA or in media containing the intracellular Ca2+ chelator BAPTA/AM. These preincubations completely blocked the bradykinin induced increase in intracellular Ca2+ but only attenuated the bradykinin mediated activation of phospholipase D. Physiological increases in intracellular Ca2+ apparently do not mediate the effect of bradykinin on phospholipase D.
Horwitz
J
J
Medical College of Pennsylvania Department of Pharmacology, Philadelphia 19129, USA.
Passarello
B
B
Corso
M
M
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology; D016716:PC12 Cells; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010739:Phospholipase D / Q000819:agonists* / Q000037:antagonists & inhibitors; D051381:Rats; D013268:Stimulation, Chemical; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D004791:Enzyme Inhibitors; D007476:Ionophores; D013729:Terpenes; D015240:Phorbol 12,13-Dibutyrate; D000431:Ethanol; D015759:Ionomycin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; D002217:Carbachol; D010739:Phospholipase D; D001920:Bradykinin; D002118:Calcium