Activation of protein kinase C (PKC) has been shown to regulate electrolyte transport in rabbit small intestine. We investigated the types of PKC isoforms in rabbit ileal villus and crypt cells and the potential for phorbol 12-myristate 13-acetate (PMA) to induce translocation of the PKC from the cytosol to the plasma membrane. Our results indicate that there are at least three PKC isoforms, alpha, epsilon and zeta, are present in both villus and crypt enterocytes. Acute treatment with PMA resulted in translocation of the PKC-alpha from the cytosol to the membrane fraction in both cell types. Prolonged exposure of the villus cells to PMA resulted in a significant progressive decrement in PKC-alpha, suggesting down regulation. Since PMA treatment results in translocation, this isoform may be involved in the regulation of electrolyte transport in the rabbit ileum.