Is protein kinase C alpha (PKCα) involved in vasopressin-induced effects on LLC-PK₁ pig kidney cells?

The involvement of protein kinase C (PKC) in vasopressin-induced effects on renal water reabsorption is still unresolved. Activation of PKC can be detected by its translocation from the cytosol (C) to the plasma membrane (PM). In LLC-PK₁ cells, the redistribution of PKCα, a predominant isoform of PKC detected, was studied utilizing western blotting after stimulation with vasopressin. Vasopressin (100 mU/ml) failed to induce a translocation of PKCα from the C to the PM. By contrast, phorbol myristate acetate (PMA, 200 nM), a potent activator of PKC, induced a relocalization of PKCα from the C to the PM. After 2 hours of treatment of cells with PMA, PKCα was predominantly detected in the PM and absent from the C. These results suggest that the signal transduction pathway of vasopressin in LLC-PK₁ cells does not involve PKCα activation and translocation.