Pentobarbital affects transepithelial electrophysiological parameters regulated by protein kinase C in rat distal colon

For rat distal colon, the transepithelial electrical parameters, short circuit current (Iscc) and transepithelial electrical resistance (TER), respectively, measure net transepithelial electrolyte transport activity and the barrier function of the epithelium. Studies with a variety of epithelial cell cultures have shown greater than 90% decreases of TER within minutes of exposure of in vitro cell sheets to phorbol esters. The phorbol ester and protein kinase C (PKC) activator, phorbol dibutyrate (PDBU), was observed to produce an over 100% elevation of Iscc but only a small yet significant 20-30% decrease of TER across rat distal colon. Inhibition of the above effects of PDBU by the PKC inhibitor bisindolylmaleimide (GFX) is further evidence that in rat distal colon, Iscc and TER are under regulatory control by PKC. When animals received anesthesia with intraperitoneal pentobarbital prior to removal of the colon, the effect of PDBU on Iscc was significantly reduced, and the effect of PDBU on TER was almost completely inhibited. This effect of pentobarbital on PKC-mediated transepithelial permeability parameters is consistent with the known ability of anesthetics to alter protein kinase C activity. Exposure of rat colon to pentobarbital produced as much as a 90% inhibition of calcium-dependent PKC activity, whereas calcium-independent activity was stimulated by as much as 35%. Prior anesthetic use may be therefore a complicating factor in observing PKC-mediated effects on epithelial barrier function using epithelial tissue models.