PHORBOL BINDING AND ENZYMATIC-ACTIVITY OF PROTEIN-KINASE-C FROM C3H 10T1/2 CELLS AND RELATION TO CONTACT INHIBITION

Protein kinase C (PKC) from membrane and cytosol fractions of fast growing as well as confluent contact-inhibited cells was assayed by two methods: PDBu binding and histone phosphorylation. In cytosol and membrane fractions of fast growing cells and in the cytosol fraction of confluent cells a reasonable agreement between the two methods was found. In membranes of confluent cells good PDBu binding was not accompanied with histone phosphorylation. Also in contact-inhibited cells, serum-stimulated hydrolysis of phosphatidylinositol bisphosphate (PIP2) was found to be reduced.