Mechanical manipulation of polymorphonuclear leukocyte plasma membranes with optical tweezers causes influx of extracellular calcium through membranechannels

Optical tweezers are used mechanically to manipulate the plasma membrane of polymophonuclear leukocytes attached to the bottom of a glass manipulation chamber. The laser trapping beam is dragged across the membrane of cells i n calcium-containing and calcium-depleted extracellular medium. This treatm ent causes a significant rise in the intracellular calcium concentration co mpared with controls, in cells in calcium-containing medium (239.8+/-49.0% against 75.4+/-16.4%, respectively), but not in cells in calcium-depleted m edium (69.1+/-9.6% against 83.4+/-18.5%, respectively), indicating that the calcium rise is caused by an influx of calcium from the environment. The r ise in calcium concentration is blocked (23.5+/-7.1% against 17.1+/-4.1%, r espectively) by the addition of lansoprazole, indicating that the influx is not due to unspecific membrane damage caused by the mechanical manipulatio n of the cell. It can therefore be concluded that mechanical manipulation o f the neutrophil membrane, in the piconewton force range exerted by the opt ical tweezer does not damage the plasma membrane but stimulates a mechanica lly inducible, membrane channel-mediated influx of extracellular calcium.