Hypoxia evokes catecholamine secretion from rat pheochromocytoma PC-12 cells.
We have monitored exocytosis of catecholamines from individual PC-12 cells by amperometry using carbon fiber microelectrodes in order to investigate possible secretory responses to acute hypoxia. In normoxia, no secretion was detected from cells perfused with a solution containing 5 mM K+. However, when [K+] was raised (10-100 mM), exocytotic events were observed. Hypoxia (PO2 11 mmHg) stimulated secretion from PC-12 cells, and in hypoxic conditions exocytosis was greater at each [K+] studied as compared with normoxia. Hypoxia-evoked secretion was abolished in Ca2+ free solutions containing 1 mM EGTA and by the non-specific Ca2+ channel blocker, Cd2+ (200 microM). Secretion was also largely inhibited by omega-conotoxin GVIA (1 microM). Exocytosis was also observed in normoxia when cells were exposed to tetraethylammonium (1-10 mM), but not 4-aminopyridine (3 mM). Our findings indicate that hypoxia evokes exocytosis via depolarization arising from inhibition of a TEA-sensitive K+ conductance, leading to Ca2+ influx primarily via N-type Ca2+ channels.
Institute for Cardiovascular Research, University of Leeds, United Kingdom.
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D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology*; D005089:Exocytosis / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D016716:PC12 Cells; D010455:Peptides / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D013111:Spider Venoms / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D020867:omega-Agatoxin IVA; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002395:Catecholamines; D010455:Peptides; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D002104:Cadmium; D019789:Tetraethylammonium; D020866:omega-Conotoxin GVIA; D009543:Nifedipine; D011188:Potassium; D002118:Calcium