Role of the proton electrochemical gradient in monoamine transport by bovine chromaffin granules.
The role of the transmembrane potential (delta phi), the proton concentration gradient (delta pH) and the proton electrochemical gradient (delta gamma H+) in monoamine uptake by bovine chromaffin granules or ghosts was investigated. In presence of ATP the permeant anion SCN- collapsed the delta phi (inside positive) and inhibited monoamine uptake by granules or well buffered ghosts. With lightly buffered ghosts, SCN- induced an acidification which resulted in a low inhibition of uptake. Cation efflux as well as anion influx affected the delta phi, and a transient valinomycin-mediated K+ efflux induced a lag in the uptake. The delta pH-driven noradrenalin uptake was also sensitive to delta phi, since superimposing a positive or a negative delta phi to the delta pH, respectively, increased or decreased the rate of noradrenalin accumulation. A delta pH was required for this increase of uptake rate, adrenalin accumulation. A delta pH was required for this increase of uptake rate, which was proportional to the delta phi. The pH-dependence of the ATP-induced monoamine uptake by granules pointed to the delta gamma H+ as the driving force. In contrast with the rate of uptake, which was not dependent on the anions present, the extent of amine incorporation was decreased when the internal anionic buffer concentration was decreased and, at a low internal buffer concentration, when ATP anion transport was blocked.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002417:Cattle; D002837:Chromaffin Granules / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials; D008744:Methylamines / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D013861:Thiocyanates / Q000494:pharmacology; D014439:Tyramine / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D008744:Methylamines; D013861:Thiocyanates; D014634:Valinomycin; D000255:Adenosine Triphosphate; D011188:Potassium; C009941:potassium thiocyanate; D009638:Norepinephrine; D014439:Tyramine