title: Phorbol ester-induced protein phosphorylation and contraction in sphincter smooth muscle of rabbit iris.
abstract: Phorbol 12,13-dibutyrate (PDBu) was employed in studies designed to determine the role of C-kinase in muscle contraction in the iris sphincter. PDBu induced MLC phosphorylation and contraction in a dose- and time-dependent manner. Maximum responses exerted by PDBu were about 50-60% of that obtained with CCh, and were totally dependent on the presence of extracellular Ca2+. PDBu had no effect on basal IP3 levels, however it blocked the CCh-stimulated accumulation of IP3. PDBu-induced effects were potentiated by ionomycin, and inhibited by the C-kinase antagonist H-7. These results provide further evidence for the involvement of C-kinase in mediating the sustained phase of the contractile response in the iris sphincter.
mesh_terms: D000818:Animals; D005136:Eye Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007498:Iris / Q000187:drug effects*; D009119:Muscle Contraction / Q000187:drug effects*; D009124:Muscle Proteins / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects; D010703:Phorbol Esters / Q000494:pharmacology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011817:Rabbits
chemical_list: D005136:Eye Proteins; D009124:Muscle Proteins; D010703:Phorbol Esters; D011493:Protein Kinase C