Selective changes in cell bodies and growth cones of nerve growth factor-differentiated PC12 cells induced by chemical hypoxia.
Cytosolic free Ca2+ concentration ([Ca2+]i) was measured in differentiated PC12 cells to test whether chemical hypoxia selectively alters intracellular Ca2+ in growth cones and cell bodies. Hypoxia increased [Ca2+]i and exaggerated its response to K+ depolarization in both parts of the cells. [Ca2+]i in the cell bodies was greater than that in the growth cones under resting conditions and in response to K+ or hypoxia. Ca2+-channel blockers selectively altered these responses. The L-channel blocker nifedipine reduced [Ca2+]i following K+ depolarization by 67% in the cell bodies but only 25% in the growth cones. In contrast, the N-channel blocker omega-conotoxin GVIA (omega-CgTX) diminished K+-induced changes in [Ca2+]i only in the growth cones. During hypoxia, nifedipine was more effective in the cell bodies than in the growth cones. During hypoxia, omega-CgTX diminished K+-induced changes by 50-75% in both parts of the cell, but only immediately after depolarization. The combination of nifedipine and omega-CgTX diminished the [Ca2+]i response to K+ with or without hypoxia by >90% in the cell body and 70% in the growth cones. Thus, the increased Ca2+ entry with K+ during hypoxia is primarily through L channels in the cell bodies, whereas in growth cones influx through L and N channels is about equal. The results show that chemical hypoxia selectively alters Ca2+ regulation in the growth cone and cell body of the same cell.
Gibson
G
G
Cornell University Medical College, Burke Medical Research Institute, White Plains, New York 10605, USA.
Toral-Barza
L
L
Zhang
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002454:Cell Differentiation; D015687:Cell Hypoxia; D004347:Drug Interactions; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009543:Nifedipine / Q000008:administration & dosage / Q000494:pharmacology; D016716:PC12 Cells / Q000378:metabolism / Q000648:ultrastructure*; D010455:Peptides / Q000008:administration & dosage / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D009414:Nerve Growth Factors; D010455:Peptides; D020866:omega-Conotoxin GVIA; D009543:Nifedipine; D011188:Potassium; D002118:Calcium