Calcium currents of neuroblastoma x glioma hybrid cells after cultivation with dibutyryl cyclic AMP and nickel.
The long-term modulation of calcium (Ca2+) currents (ICa) was studied in 108CC15 neuroblastoma x glioma hybrid (NxG) cells grown under various culture conditions. The following results were obtained: 1. Addition of 1 mM dibutyryl cyclic adenosine monophosphate (db-cAMP) or 0.1 microM forskolin to the culture medium increased a transient component of ICa two-fold within 3 days, from 21.0 +/- 1.6 pA/pF (n = 22) to a maximum of 40.0 +/- 2.6 pA/pF (n = 28). Under these conditions, cells also expressed a slowly inactivating ICa component (maximum after 3 days, 20.5 +/- 1.6 pA/pF, n = 28). 2. The fast inactivating ICa as well as the db-cAMP-induced slowly inactivating ICa were completely down-regulated during incubation of NxG cells with the inorganic Ca2+ channel blocker, nickel (Ni2+, 100 microM). The suppressing effect was reversed within 3 days of incubation in db-cAMP-containing medium lacking Ni2+. 3. Binding studies on membrane preparations of control and Ni2(+)-pretreated NxG cells revealed a marked difference in the maximal (+)3H-PN200-110 binding. The difference was seen in undifferentiated as well as in db-cAMP-incubated cells. 4. The protein synthesis blocker, cycloheximide, suppressed both the db-cAMP-induced increase and the reappearance of ICa following Ni2+ pretreatment. It is suggested that chronic application of db-cAMP or Ni2+ to NxG cells increases and decreases the number of Ca2+ channel proteins, respectively.
Eckert
R
R
II. Physiologisches Institut, Universität des Saarlandes, Homburg/Saar, Federal Republic of Germany.
Hescheler
J
J
Krautwurst
D
D
Schultz
G
G
Trautwein
W
W
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D005910:Glioma / Q000503:physiopathology*; D006822:Hybrid Cells / Q000502:physiology; D017275:Isradipine; D051379:Mice; D009447:Neuroblastoma / Q000503:physiopathology*; D009532:Nickel / Q000494:pharmacology*; D010069:Oxadiazoles / Q000378:metabolism; D051381:Rats; D014407:Tumor Cells, Cultured
D015220:Calcium Channels; D010069:Oxadiazoles; D005576:Colforsin; D003994:Bucladesine; D009532:Nickel; D003513:Cycloheximide; D017275:Isradipine