Isozyme-specific inhibitors of protein kinase C translocation: effects on contractility of single permeabilized vascular muscle cells of the ferret

1. The effects on contractility of three peptides reported to inhibit protein kinase C (PKC) translocation in an isozyme-specific manner were studied: a peptide from the C2 domain of conventional PKCs (C2-2), a peptide from the N-terminal variable domain of epsilon PKC (epsilon V1-2) and a peptide (ABP) from the actin-binding domain of epsilon PKC (epsilon(223-228)). 2. Isometric force was directly recorded from individual hyperpermeable ferret por tal vein or aortic smooth muscle cells. 3. Phenylephrine contracted permeabilized portal vein cells at pCa 6.7 but not at pCa 7.0. However, phenylephrine did contract aortic cells at pCa 7.0 4. C2-2 inhibited phenylephrine-induced contraction, but did not affect resting tension, in portal vein cells at pCa 6.7. In aortic cells at either, pC 6.7 or 7.0, C2-2 had no effect on either basal tension or phenylephrine-induced contraction. 5. ABP did not evoke any changes in phenylephrine-induced contraction or baseline tension in either portal vein or aortic cells. 6. epsilon V1-2 inhibited phenylephrine-induced contraction and decreased resting tension in aortic cells at pCa 7.0, but nut in portal vein cells at pCa 6.7. 7. Western blots indicated that portal vein cells contained substantially more alpha PKC than aortic cells. Portal vein cells also contained small amounts of beta PKC, which was undetectable in aortic cells. In contrast, aortic cells contained more epsilon PKC than portal vein cells. Even though epsilon PKC was expressed in por tal vein and alpha PKC in aorta, imaging studies indicated that they were not translocated in these cell types. 8. These results suggest that the Ca2+-dependent isozymes of PKC (alpha and/or beta) play a major role in contraction of the por tal vein but not of the aorta. In contrast, the results are consistent with epsilon PKC, but not Ca2+-dependent PKC isozymes, regulating contractility of the aorta.