Different Membrane Pathways Mediate Ca2+ Influx in Adrenal Chromaffin Cells Exposed to 150–400 ns Electric Pulses. (29th March 2018) - Bagalkot, Tarique R.
Abstract : Exposing adrenal chromaffin cells to 5 ns electric pulses (nsPEF) causes a rapid rise in intracellular Ca 2+ (C a 2 + i ) that is solely the result of Ca 2+ influx through voltage-gated Ca 2+ channels (VGCCs). This study explored the effect of longer duration nsPEF onC a 2 + i . Single 150, 200, or 400 ns pulses at 3.1 kV/cm evoked rapid increases inC a 2 + i, the magnitude of which increased linearly with pulse width and electric field amplitude. Recovery ofC a 2 + i to prestimulus levels was faster for 150 ns exposures. Regardless of pulse width, no rise inC a 2 + i occurred in the absence of extracellular Ca 2+, indicating that the source of Ca 2+ was from outside the cell. Ca 2+ responses evoked by a 150 ns pulse were inhibited to varying degrees by ω -agatoxin IVA, ω -conotoxin GVIA, nitrendipine or nimodipine, antagonists of P/Q-, N-, and L-type VGCCs, respectively, and by 67% when all four types of VGCCs were blocked simultaneously. The remaining Ca 2+ influx insensitive to VGCC inhibitors was attributed to plasma membrane nanoporation, which comprised theE -field sensitive component of the response. Both pathways of Ca 2+ entry were inhibited by 200 μ M Cd 2+ . These results demonstrate that, in excitable chromaffin cells, single 150–400 ns pulses increased the permeability of the plasma membrane to Ca 2+ in addition to causing Ca 2+ influx via VGCCs.