Anti-peptide antibodies specific for each protein kinase C (PKC) isozyme were used to screen SK-N-SH human neuroblastoma cells. These cells were found to express only alpha- and zeta-PKC. Stimulation of these cells with phorbol esters caused alpha- but not zeta-PKC to translocate from cytosolic to membrane fractions. Stimulation of these cells with carbachol, which releases inositol trisphosphate and diacylglycerol, caused a transient translocation of alpha-PKC but not of zeta-PKC. Carbachol did, however, cause a gradual increase in immunoreactive zeta-PKC which reached maximal values 10-20 min after stimulation. These results implicate zeta-PKC in a receptor-mediated signalling event.