Effect of Phorbol Esters on the Distribution and Total Activity of Protein Kinase C in the Perfused Rat Heart

1. 1. The perfused rat heart was treated with the tumour-promoter and protein kinase C activator, phorbol 12-myristate 13-acetate and the distribution of protein kinase C activity between cytosolic and particulate fractions determined. 2. 2. Phorbol ester treatment led to a rapid loss of protein kinase C activity from the cytosol (t0.5 = 2 min) with a corresponding translocation into the particulate fraction. Translocated protein kinase C activity was tightly bound to the particulate fraction, could only be extracted with buffers containing 2% Triton X-100 and could therefore be misinterpreted as being down-regulated. 3. 3. Claims of rapid down-regulation of protein kinase C activity by phorbol esters need to be supported by rigorous procedures for extraction of the partieulate material. © 1989.