Contrasting effects of phorbol dibutyrate and phorbol myristate acetate in rabbit aorta |
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Authors: | R Villalobos-Molina V Ransanz M E Torres-Márquez E Hong J A García-Sáinz |
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Affiliation: | Depto. de Farmacología, CINVESTAV-IPN, Mexico, D.F. |
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Abstract: | In rat hepatocytes, active phorbol esters inhibited the alpha 1-adrenergic stimulation of phosphatidylinositol labeling with the expected potency order: phorbol myristate acetate (PMA) greater than phorbol dibutyrate (PDB). In contrast, in rabbit aorta the alpha 1-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. |
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