Hypertonic activation of a non-selective cation conductance in HeLa cells and its contribution to cell volume regulation

In whole-cell recordings on single HeLa cells, the hypertonic activation of a cation conductance with a selectivity ratio P_Na:P _Li:P_K:P_Cs:P_NMDG:P _Ca:P_Cl of 1.00:0.86:0.84:0.56:0.10:0.07:0.15 was observed. This (non-selective) cation conductance was reduced to 59 and 30% of maximal stimulation by Gd³⁺ and flufenamate, respectively, but it was insensitive to amiloride (with each compound applied at 100 μmol/l). As was determined by the Coulter counter technique, the cation conductance was the main mechanism of regulatory volume increase (RVI) in HeLa cells. Whereas a significant contribution of Na⁺/H⁺ antiport was also detectable, Na⁺-K⁺-2Cl^- symport most likely did not contribute to RVI.