Protein kinase C isoenzymes in rat and human cardiovascular tissues

1 We have compared the expression of protein kinase C (PKC) activity and immune-detectable isoenzymes in cytosolic and membrane extracts of rat and human cardiovascular tissues (heart, kidney, aorta, saphenous vein). Experiments were performed in raw extracts and upon combined diethylaminoethylcellulose (DEAE) and phenylsepharose column chromatography. 2 PKC activity that bound to DEAE mostly eluted with 200 mM NaCl. DEAE-purified PKC from all tissues except rat kidney bound almost quantitatively to phenylsepharose and eluted with 0.5-0 M NaCl. 3 Immunoblots with an antibody against classical PKCs and the activator profile for phosphatidylserine, diolein and Ca2+ revealed that the PKC from rat kidney, which did not bind to phenylsepharose, was most probably due to a proteolytically-generated, constitutively active PKC which is not under the control of a regulatory subunit. 4 Studies in the reference tissue, rat brain, demonstrated that all PKC isoenzymes investigated (classical PKCs alpha, beta, gamma, new PKCs delta, epsilon, eta, theta, and atypial PKCs zeta, lambda, iota) have similar DEAE and phenylsepharose chromatography elution profiles. In the functional assay an inhibitor of all known PKC isoenzymes, bisindolylmaleimide, and a specific inhibitor of classical PKCs, Go-- 6976, both inhibited PKC from rat brain completely and with high potency indicating that the functional assay preferentially detects classical PKC isoenzymes. 5 Each PKC isoenzyme had a tissue-specific expression profile which was similar in rat and man. The classical PKC alpha, the new PKCs delta and epsilon and all atypical PKCs were detectable in most tissues, whereas the PKC beta and PKC gamma were not detected in any pheripheral tissue; PKC eta and PKC theta were found in some tissues. 6 We conclude that combined DEAE and phenylsepharose chromatography is useful to enrich and detect PKC isoenzymes; no major species differences in tissues-specific expression patterns appear to exist between rat and man.