ABSTRACT—In the basal state, the presence of L pyruvate kinase (LPK) was constantly observed in primary human liver cell cultures initiated from explants, when cells were examined by immunofluorescence and double labelling. After short‐term insulin incubation, M pyruvate kinase (MPK) appeared. Therefore, both LPK and MPK were located in the same cells. We previously obtained the same results in isolated rat hepatocytes in which we demonstrated that short‐term regulation of M2PK by insulin was a function of dose and/or incubation time. The present work established that similar conditions govern the regulation of this isozymein vitroin human hepato