CONTROL OF THE AMILORIDE-SENSITIVE NA-PROTEIN( CURRENT IN MOUSE SALIVARY DUCTS BY INTRACELLULAR ANIONS IS MEDIATED BY A G)

1. We have previously reported that the Na+ conductance in mouse intra lobular salivary duct cells is controlled by cytosolic anions, being i nhibited by high cytosolic concentrations of Cl- and NO3- but not of g lutamate. In the present paper, we use whole-cell patch-clamp methods to investigate whether this anion effect is mediated by a G protein. 2 . Inclusion of 100 mu mol l(-1) GTP-gamma-S, a non-hyrdrolysable GTP a nalogue, in the glutamate-containing pipette solution, i.e. when the N a+ conductance is active, reduced the size of the Na+ conductance wher eas inclusion of 100 mu mol l(-1) GDP-beta-S, a non-hydrolysable GDP a nalogue, had no effect. 3. Inclusion of 100 mu mol l(-1) GDP-beta-S in the NO3--containing pipette solution, i.e. when the Na+ conductance i s inhibited, reactivated the conductance. Inclusion of 500 ng ml(-1) a ctivated pertussis toxin in the NO3--containing pipette solution had a similar effect on the Na+ conductance. 4. We conclude that the inhibi tory effect of intracellular anions such as NO3- and Cl- on the amilor ide-sensitive Na+ conductance in mouse mandibular intralobular duct ce lls is mediated by a G protein sensitive to pertussis toxin.