One of the primary events in the regulatory volume increase of rat hepatocytes is the activation of an amiloride-sensitive Na conductance, a process mediated by PKC. Here, the actual PKC isoform employed was specified and some of the mechanisms further upstream were defined.
Activation of Na conductance was Ca independent and, under isotonoc conditions, it could be mimicked by indolactam V. Because the nPKCs expressed in rat hepatocytes are δ and ε, and ε did not respond to hypertonicity, this renders PKCδ the most likely isoform that mediates activation of Na conductance. This could be confirmed with immunoblots and by use of a specific PKCδ activator.
The hypertonic activation of Na conductance was inhibited by genistein, pertussis toxin and wortmannin indicative that tyrosin kinases, Gi and/or Go proteins and PI3-kinase are part of the signaling cascade. Activation was also blocked by the microtubule-disruptor nocodazole which may suggest that exocytotic insertion of channels into the plasma membrane plays an additional (constitutive) role in the activation process. (This abstract is as it is printed in the abstract issue of the journal).