Contrasting effects of phorbol dibutyrate and phorbol myristate acetate in rabbit aorta
Villalobos-Molina, R.; Ransanz, V.; Torres-Márquez, M.E.; Hong, E.; García-Sáinz, J.A.
Biochemical and Biophysical Research Communications 171(2): 618-624
In rat hepatocytes, active phorbol esters inhibited the alpha1-adrenergic stimulation of phosphatidylinositol labeling with the expected potency order: phorbol myristate acetate (PMA) > phorbol dibutyrate (PDB). In contrast, in rabbit aorta the alpha1-adrenergic action was inhibited dose-dependently by PDB but not by PMA. Similarly PDB (but not PMA) induced a strong contraction in rabbit aorta. The phorbol ester-induced contraction developed slowly, was dose-dependent and independent of extracellular calcium. These effects of PDB in rabbit aorta were neither inhibited by the protein kinase inhibitor H-7 nor mimicked by the synthetic diacylglycerol, OAG. Our results raise some doubts on the mechanism(s) through which the actions of PDB take place in rabbit aorta.