Calcium-dependent inhibition of L, N, and P/Q Ca2+ channels in chromaffin cells: role of mitochondria.
The hypothesis that the buffering of Ca(2+) by mitochondria could affect the Ca(2+)-dependent inhibition of voltage-activated Ca(2+) channels, (I(Ca)), was tested in voltage-clamped bovine adrenal chromaffin cells. The protonophore carbonyl cyanide m-chlorophenyl-hydrazone (CCCP), the blocker of the Ca(2+) uniporter ruthenium red (RR), and a combination of oligomycin plus rotenone were used to interfere with mitochondrial Ca(2+) buffering. In cells dialyzed with an EGTA-free solution, peak I(Ca) generated by 20 msec pulses to 0 or +10 mV, applied at 15 sec intervals, from a holding potential of -80 mV, decayed rapidly after superfusion of cells with 2 microm CCCP (tau = 16.7 +/- 3 sec; n = 8). In cells dialyzed with 14 mm EGTA, CCCP did not provoke I(Ca) loss. Cell dialysis with 4 microm ruthenium red or cell superfusion with oligomycin (3 microm) plus rotenone (4 microm) also accelerated the decay of I(Ca). After treatment with CCCP, decay of N- and P/Q-type Ca(2+) channel currents occurred faster than that of L-type Ca(2+) channel currents. These data are compatible with the idea that the elevation of the bulk cytosolic Ca(2+) concentration, [Ca(2+)](c), causes the inhibition of L- and N- as well as P/Q-type Ca(2+) channels expressed by bovine chromaffin cells. This [Ca(2+)](c) signal appears to be tightly regulated by rapid Ca(2+) uptake into mitochondria. Thus, it is plausible that mitochondria might efficiently regulate the activity of L, N, and P/Q Ca(2+) channels under physiological stimulation conditions of the cell.
Hernandez-Guijo
J M
JM
Instituto Teófilo Hernando, Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain.
Maneu-Flores
V E
VE
Ruiz-Nuno
A
A
Villarroya
M
M
Garcia
A G
AG
Gandia
L
L
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000187:drug effects / Q000378:metabolism; D020865:Calcium Channels, P-Type / Q000187:drug effects / Q000378:metabolism; D020907:Calcium Channels, Q-Type / Q000187:drug effects / Q000378:metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000031:analogs & derivatives / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism; D007476:Ionophores / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011978:Receptors, Nicotinic / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D015222:Sodium Channels / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D002614:Chelating Agents; D007476:Ionophores; D009840:Oligomycins; D011978:Receptors, Nicotinic; D015222:Sodium Channels; D012402:Rotenone; D012430:Ruthenium Red; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002118:Calcium