Abstract
ATP, 3'-O-(4-benzoyl)benzoyl-ATP (BzATP), a photoaffinity analog on ATP, and several other ATP analogs induced an increase in plasma membrane permeability to monovalent ions and normally impermeant metabolites, including nucleotides, in transformed 3T6 mouse fibroblasts. Photoincorporation of BzATP was inhibited by ATP, ATP alpha S, ATP gamma S, and other ATP analogs that induced an increase in plasma membrane permeability to nucleotides in 3T6 cells under nonphotoactivating conditions. GTP, ITP, UTP, adenosine, and ATP analogs that did not alter plasma membrane permeability to nucleotides under nonphotoactivating conditions also had no effect on BzATP photoincorporation. Photoincorporation of BzATP was also modulated by the osmolarity and the divalent cation concentration of the assay medium. The increase in plasma membrane permeability to nucleotides induced by photoincorporated BzATP occurred at the same rate and had the same temperature, pH, ionic strength, and divalent cation requirements as the increase in plasma membrane permeability to nucleotides induced by ATP and BzATP under nonphotoactivating conditions. These findings support the hypothesis that BzATP can be covalently incorporated into a P sub(2) purinoceptor in 3T6 cells that is coupled to plasma membrane channels for ions and other metabolites.