The role of specific PKC isoforms in the regulation of epithelial Cl^- secretion by Ca²⁺-dependent secretagogues remains controversial. In the developing rabbit distal colon, the bile acid taurodeoxycholate (TDC) acts via [Ca²⁺]_i to stimulate Cl^- transport in adult, but not in young, animals, whereas the PKC activator, phorbol dibutyrate (PDB), stimulates Cl^- transport at all ages. We tested the hypothesis that specific PKC isoforms account for the age-specific effects of TDC. The effects of conventional and novel PKC-specific inhibitors on TDC- and PDB-stimulated Cl^- transport in adult and weanling colonocytes were assessed using 6-methoxy-quinolyl acetoethyl ester. In adult colonocytes, the cPKC inhibitor Go6976 inhibited PDB, but not TDC action, whereas the cPKC and nPKC inhibitor Go6850 blocked both TDC and PDB action. The PKC-specific inhibitors peptide (V1-1) and rottlerin, inhibited TDC- and PDB- stimulated Cl^- transport in adult colonocytes. Rottlerin also decreased TDC-stimulated short-circuit current in intact colonic epithelia. Only Go6976, but neither rottlerin nor V1-1 inhibited PDB-stimulated transport in weanling colonocytes. Colonic lysates express PKC- and-protein equally at all ages but not PKCor - at any age. Expression of PKCand PKCprotein was newborn>adult>weanling, but PKC was expressed in adult but not in weanling or newborn colonocytes. TDC (1.6-fold) and PDB (2.0-fold) stimulated PKC enzymatic activity in adult but failed to do so in weanling colonocytes. PKCmRNA expression showed age-dependence. Thus, PKCis critical for the action of TDC in the adult colon, and its low expression in young animals accounts for their inability to secrete in response to bile acids.