Submicrosecond intense pulsed electric field effects on intracellular free calcium: mechanisms and effects

Application of submicrosecond intense pulsed electric fields (sm/i-PEF) to cells results in rapid, transient rises in intracellular free calcium concentrations ([Ca/sup ++/]/sub i/) in human blood neutrophils, human promyelocytic leukemia cells (HL60), and human T-cell leukemia cells (Jurkat cells). The magnitude of the rise in [Ca/sup ++/]/sub i/ in human neutrophils is related to the intensity of applied sm/i-PEF. Some 10-50% of the rise in [Ca/sup ++/]/sub i/ triggered by 300-ns pulses is due to release of Ca/sup ++/ from intracellular sources, while maximally 10% of the rise in [Ca/sup ++/]/sub i/ triggered by 60-ns pulses is due to release from intracellular sources. Repetition of a sm/i-PEF application of lesser intensity than the first pulse fails to induce a rise in [Ca/sup ++/]/sub i/, while a second pulse of equal or greater intensity elicits a small or moderate rise, respectively. When sm/i-PEF applications were examined for effects on cellular function, no effect was observed on neutrophil phagocytosis. Suppression of spontaneous H/sub 2/O/sub 2/ production was observed after a 300-ns, 60-kV/cm pulse, and transient suppression of neutrophil chemotaxis was observed following a 300-ns and 60-ns, 60-kV/cm pulse. No evidence of proton influx/efflux was found following sm/i-PEF application. sm/i-PEF applications may allow manipulation of selected cell behaviors/function based on their ability to initiate changes in [Ca/sup ++/]/sub i/.