title: Phorbol esters inhibit alpha 1-adrenergic receptor-stimulated phosphoinositide hydrolysis and contraction in rat aorta: evidence for a link between vascular contraction and phosphoinositide turnover.
abstract: We investigated the actions of two biologically active phorbol esters, phorbol dibutyrate (PDB) and phorbol myristate acetate (PMA), on receptor-stimulated phosphoinositide hydrolysis in rat aorta. We found both PDB and PMA potently inhibited norepinephrine (NE) stimulated PI hydrolysis in rat aortic rings. The biologically inactive phorbol, 4-alpha-phorbol was ineffective. In the presence of the calcium channel antagonist nitrendipine, PDB potently inhibited both the phasic and tonic components of NE-induced contraction. These results suggest a functional coupling between receptor-stimulated PI turnover and vascular contraction. They also suggest a mode of feed-back regulation in vascular tissue involving phorbol esters in receptor-stimulated PI hydrolysis.
mesh_terms: D000818:Animals; D006868:Hydrolysis; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D009568:Nitrendipine; D009638:Norepinephrine / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D014666:Vasomotor System / Q000187:drug effects*
chemical_list: D010703:Phorbol Esters; D010716:Phosphatidylinositols; D011942:Receptors, Adrenergic, alpha; D009568:Nitrendipine; D009543:Nifedipine; D009638:Norepinephrine