title: Protein kinase-C mediates dual modulation of L-type Ca2+ channels in human vascular smooth muscle.
abstract: The role of protein kinase C (PKC) in cellular regulation of L-type Ca2+ channels was investigated in human umbilical vein smooth muscle. Activation of PKC, by low concentrations (< 30 nM) of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) caused inhibition of Ca2+ channels, while higher concentrations of TPA (> 100 nM) elicited a transient rise, followed by sustained inhibition of Ca2+ channel activity in cell-attached patches. Low TPA concentrations predominantly reduced channel availability, while high concentrations of TPA (100 nM) transiently increased channel availability and, in addition, prolonged mean open time. The inactive 4-alpha-phorbol-12,13- didecanoate failed to affect channel activity, and pretreatment of the cells with PKC inhibitors (H-7, chelerythrine) antagonized inhibitory and stimulatory effects of TPA. Our results provide evidence for two distinct PKC-dependent mechanisms of L-type Ca2+ channel regulation in smooth muscle.
authors.affiliation: Institut für Pharmakologie und Toxikologie, Universität Graz, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Schuhmann
authors.forename: K
authors.initials: K
authors.lastname: Groschner
mesh_terms: D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate