title: Phorbol-ester-induced alterations of free calcium ion transients in single rat hepatocytes.
abstract: The effect of the phorbol esters phorbol 12-myristate 13-acetate (TPA) and phorbol 12,13-dibutyrate (PDB) on changes in free Ca2+ concentration ([Ca2+]i) in single rat hepatocytes, microinjected with the photoprotein aequorin, were investigated. [Arg8]vasopressin and phenylephrine induced a series of repetitive [Ca2+]i transients. Phorbol esters inhibited the alpha 1-adrenoceptor-induced response; sub-nanomolar concentrations decreased the transient frequency, and higher concentrations abolished the transients. The inhibitory effect of PDB was readily reversible. Phorbol esters were less effective in decreasing the frequency of [Arg8]-vasopressin-induced transients, and the inhibition could be overcome by high [Arg8]vasopressin concentrations.
mesh_terms: D000331:Aequorin; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000493:pharmacokinetics*; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D010703:Phorbol Esters; D001127:Arginine Vasopressin; D010656:Phenylephrine; D015240:Phorbol 12,13-Dibutyrate; D000331:Aequorin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium