Role of cell volume and protein kinase C in regulation of a Cl- conductance in single proximal tubule cells of Rana temporaria.

1. The whole-cell patch clamp technique was used to investigate Cl- currents in single proximal tubule cells isolated from kidneys of Rana temporaria. 2. Immediately following establishment of the whole-cell clamp, the Cl- conductance (gCl) of the cells was low. However, with 2 mM ATP in the pipette there was a time-dependent activation of gCl. Such activation was inhibited when the bath contained a hypertonic Ringer solution. 3. The Cl- conductance was not directly dependent on cell volume; gCl increased with hypotonic shock and decreased with hypertonic shock, but only in the presence of ATP. 4. Activation of gCl by ATP was dependent on extracellular Ca2+; however, the conductance was not directly Ca2+ sensitive. Activation was inhibited by Gd3+, which also had a direct inhibitory action on gCl. 5. Inhibition of protein kinase C (PKC), by 10 microM PKC pseudo-substrate (PKC-ps), completely abolished the ATP-dependent activation of gCl, while stimulation of PKC, by the PKC activator 4 beta-phorbol 12-myristate, 13-acetate (PMA), increased the degree of activation typically observed with ATP. 6. We propose that gCl is activated by PKC-mediated phosphorylation and plays a role in volume regulation of the cells.