[Regulation by ATP of a phospholipase D in the ductal cells of the submaxillary gland].

ATP increased the PLD activity of rat submandibular ductal cells in a concentration-dependent and calcium-sensitive manner. Among ATP analogs, BZATP and ATPgammaS were the only ones able to stimulate the PLD activity. ATP and BZ-ATP also activated PLD in control mice, but not in mice lacking the P2X7 receptors. Oxidized ATP, Coomassie blue, NiCl2 and MgCl2 inhibited the response to ATP. PLD stimulation by ATP was inhibited by calphostin C and chelerythrine, two PKC inhibitors. The PLD stimulation by BZ-ATP and TPA, a phorbol ester which activates PKC, were not additive. Purinergic agonists did not increase the phosphorylation of proteins on tyrosyl residues. We can conclude that the activation of P2X7 receptors in rat submandibular glands ductal cells, is coupled to the activation of PLD. This activation is partly mediated by PKC and is not secondary to the activation of a tyrosine kinase.