Cation conductance regulated by ambient Cl- in cultured rat mesangial cells

Several functions of mesangial cells, such as contraction and release of nitric oxide, are dependent on the ambient Cl- concentration. Herein we describe a direct effect of Cl- on mesangial cell membrane conductance. Rat mesangial cells were isolated, cultured, and were patch-clamped in the whole-cell configuration. The external concentration - ([Cl-]o) - of standard Ringer's solutions was changed isotonically from standard of 160 mM to 35 mM while cell membrane conductance was continuously recorded. Results indicated that control I-V curves of the steady state current had a linear slope conductance of 0.95 nS (n = 10, r = 0.9). In low [Cl-]o, conductance outwardly rectified and increased to 4.1 nS between -120 and 0 mV and to 16.8 nS between 0 and 40 mV (n = 10, r = 0.9; p<0.01). The increase in conductance occurred within a few seconds and was reversible. Our results show that a large mesangial cell membrane conductance for cations is activated upon exposure to low [Cl-]o.