Depletion of intracellular calcium stores triggers transplasmamembrane chloride influx in human lymphocytes: regulation by tyrosine kinase.

The capacitative regulation of intracellular chloride concentration ([Cl-]i) was measured in intact human lymphocytes using the Cl(-)-sensitive fluorescence dye 6-methoxy-1-(3-sulfonato-propyl)-quinolinium (SPQ). The fluorescence was measured at 433 nm with the excitation wavelength of 344 nm. The emptying of intracellular Ca2+ stores after the specific inhibition of the endoplasmic Ca2+ ATPase by thapsigargin produced a concentration-dependent transplasmamembrane Cl- influx. The thapsigargin-induced Cl- increase was also seen in the absence of extracellular Ca2+, but it was significantly reduced after the addition of the Cl- exchange blocker, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. The thapsigargin-induced Cl- increase was significantly reduced after the specific inhibition of tyrosine kinase by genistein or tyrphostin A25. It is concluded that the depletion of intracellular Ca2+ pools triggers transplasmamembrane Cl- influx by a tyrosine kinase-dependent mechanism.