[Changes in K+, Na+ and Cl- contents and K+ and Cl- fluxes during apoptosis of U937 cells by staurosporine. On the mechanism of cell dehydration in apoptosis].

K+, Na+ and Cl- balance and K+ (Rb+) and 36Cl fluxes in during apoptosis of U937 cells caused by 0.2 or 1 microM staurosporine were studied by flame emission and radiotracer techniques. It is found that monovalent ion redistribution accounts for 2/3 of all decrease in the amount of intracellular osmolytes in apoptotic cells while 1/3 is due to the loss of other intracellular osmolytes. Na+ gain in apoptotic cells hampers dehydration is caused by K+ and Cl- loss. It is found that the rate of equilibration of 36Cl, Rb+ (K+) and 22Na+ between cells and the medium exceeds significantly the rate of alteration of cell ion content associated with apoptosis. It is concluded that apoptotic changes should be considered as a drift of the balanced ion distribution. Alteration of the ion balance in apoptosis, caused by 0.2 microM staurosporine, is associated with an increase in the uabain-resistant Rb+ (K+) "channel" influx and insignificant alteration of the uabain-sensitive "pump" influx. Stronger apoptosis, induced by 1 microM staurosporine, is associated with a decrease in the pump fluxes and insignificant changes in the "channel" Rb+ (K+) fluxes. Decreasing of the Cl- level in apoptotic cells by a factor 1.4-1.8 is accompanied with a decrease in the flux, by a factor 1.2-1.6.