Extracellular nucleotides stimulate receptor-mediated calcium mobilization and inositol phosphate production in human fibroblasts.
In human skin fibroblasts, low concentrations of extracellular ATP stimulated 45Ca2+ efflux from a slow-turnover intracellular pool, accompanied by inositol phosphate generation. These effects of ATP were not due to a generalized increase in plasma-membrane permeability. The EC50 (concn. giving 50% stimulation) for ATP was dependent on Ca2+ and Mg2+ concentrations in a manner which indicates that a form of ATP uncomplexed with bivalent cations is the active species. The rank order of potency of nucleotides was: ATP = UTP greater than adenosine 5'-[gamma-thio]triphosphate greater than ITP greater than ADP greater than UDP greater than other nucleoside triphosphates. Adenosine 5'-[alpha beta-methylene]triphosphate, adenosine 5'-[beta gamma-methylene]triphosphate and 2-methylthio-ATP were inactive. Thus the nucleotide specificity of this receptor is different from that of previously characterized P2 purinoceptors. Nucleotide-stimulated 45Ca2+ mobilization and inositol phosphate production were markedly inhibited by phorbol ester, and partially inhibited by pertussis-toxin pretreatment. These findings suggest that the coupling of nucleotide receptor to phospholipase C is mediated both by a pertussis-toxin-sensitive G-protein and by a pertussis-toxin-insensitive mechanism.
Fine
J
J
Department of Chemical Pathology, University of Cape Town Medical School, South Africa.
Cole
P
P
Davidson
J S
JS
D000255:Adenosine Triphosphate / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D009711:Nucleotides / Q000494:pharmacology*; D037342:Pertussis Toxin; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007295:Inositol Phosphates; D009711:Nucleotides; D011983:Receptors, Purinergic; D010566:Virulence Factors, Bordetella; D000255:Adenosine Triphosphate; D037342:Pertussis Toxin; D008274:Magnesium; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D014544:Uridine Triphosphate