Release of dopamine and norepinephrine by hypoxia from PC-12 cells.
We examined the effects of hypoxia on the release of dopamine (DA) and norepinephrine (NE) from rat pheochromocytoma 12 (PC-12) cells and assessed the involvement of Ca2+ and protein kinases in stimulus-secretion coupling. Catecholamine release was monitored by microvoltammetry using a carbon fiber electrode as well as by HPLC coupled with electrochemical detection (ECD). Microvoltammetric analysis showed that hypoxia-induced catecholamine secretion (PO2 of medium approximately 40 mmHg) occurred within 1 min after the onset of the stimulus and reached a plateau between 10 and 15 min. HPLC-ECD analysis revealed that, at any level of PO2, the release of NE was greater than the release of DA. In contrast, in response to K+ (80 mM), DA release was approximately 11-fold greater than NE release. The magnitude of hypoxia-induced NE and DA releases depended on the passage, source, and culture conditions of the PC-12 cells. Omission of extracellular Ca2+ or addition of voltage-gated Ca2+ channel blockers attenuated hypoxia-induced release of both DA and NE to a similar extent. Protein kinase inhibitors, staurosporine (200 nM) and bisindolylmaleimide I (2 microM), on the other hand, attenuated hypoxia-induced NE release more than DA release. However, protein kinase inhibitors had no significant effect on K+-induced NE and DA releases. These results demonstrate that hypoxia releases catecholamines from PC-12 cells and that, for a given change in PO2, NE release is greater than DA release. It is suggested that protein kinases are involved in the enhanced release of NE during hypoxia.
Kumar
G K
GK
Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Overholt
J L
JL
Bright
G R
GR
Hui
K Y
KY
Lu
H
H
Gratzl
M
M
Prabhakar
N R
NR
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D015687:Cell Hypoxia; D002470:Cell Survival; D002851:Chromatography, High Pressure Liquid; D004298:Dopamine / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D008839:Microelectrodes; D009638:Norepinephrine / Q000378:metabolism*; D010100:Oxygen / Q000008:administration & dosage; D016716:PC12 Cells / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D019311:Staurosporine / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D007211:Indoles; D008301:Maleimides; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D019311:Staurosporine; C088060:bisindolylmaleimide; D011188:Potassium; D010100:Oxygen; D004298:Dopamine; D009638:Norepinephrine