Ba2+-induced ATP release from adrenal medullary chromaffin cells is mediated by Ba2+ entry through both voltage- and receptor-gated Ca2+ channels.
We have measured on-line the exocytotic secretion of ATP from adrenal medullary chromaffin cells induced by Ba2+ using a luciferin/luciferase assay. We have found that Ba2+-induced ATP release requires the entry of Ba2+ through either voltage- or receptor-gated Ca2+ channels. This conclusion is based on the observations that short preincubations with low concentrations of either nicotine or K+ greatly enhance Ba2+-induced ATP release and that this augmentation can be blocked with the nicotinic receptor antagonist, hexamethonium, and the Ca2+ antagonist, nifedipine, respectively. Moreover, both nicotine and K+ stimulate 133Ba2+ uptake, which in the case of K+ is inhibited by nifedipine. These results support the hypothesis that the cellular events leading to Ba2+-induced secretion coincide at least in part with the events leading to Ca2+-dependent exocytosis.
Forsberg
E J
EJ
Laboratory of Cell Biology and Genetics, National Institutes of Health, Bethesda, MD 20892.
Pollard
H B
HB
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D001464:Barium / Q000493:pharmacokinetics / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism* / Q000502:physiology; D002417:Cattle; D049454:Firefly Luciferin; D005456:Fluorescent Dyes; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
D015220:Calcium Channels; D005456:Fluorescent Dyes; D006584:Hexamethonium Compounds; D011978:Receptors, Nicotinic; D001464:Barium; D018738:Hexamethonium; D049454:Firefly Luciferin; D009538:Nicotine; D000255:Adenosine Triphosphate; D009543:Nifedipine; D011188:Potassium