Role of a transmembrane pH gradient in epinephrine transport by chromaffin granule membrane vesicles.

AUTOR(ES)

Schuldiner, S

RESUMO

ATP-driven transport and accumulation of epinephrine in chromaffin granule membrane vesicles isolated from bovine adrenal medulla is inhibited by the proton ionophores carbonylcyanide p-trifluoromethoxyphenylhydrazone and nigericin, but not by valinomycin. Moreover, an artificially imposed pH gradient (interior acid) is able to drive this reserpine-sensitive transport system in the absence of ATP. Dicyclohexylcarbodiimide, an inactivator of the chromaffin granule membrane-bound ATPase, completely inhibits ATP-dependent epinephrine accumulation, but has much less effect when an imposed pH gradient is the driving force for epinephrine transport. The findings provide a strong indication that a pH gradient (interior acid) is the immediate driving force for epinephrine uptake in these storage granules and suggest that ATP-driven epinephrine transport is the result of two processes: (i) generation of a proton electrochemical gradient (interior acid and positive) by the membrane-bound, proton-translocating ATPase; and (ii) pH gradient-driven accumulation of the catecholamine.

Documentos Relacionados

• pH gradient-stimulated transport of urate and p-aminohippurate in dog renal microvillus membrane vesicles.
• The transmembrane pH gradient drives uphill folate transport in rabbit jejunum. Direct evidence for folate/hydroxyl exchange in brush border membrane vesicles.
• Membrane growth can generate a transmembrane pH gradient in fatty acid vesicles
• Role of transmembrane pH gradient and membrane binding in nisin pore formation.
• pH gradient effects on chloride transport across basolateral membrane vesicles from guinea-pig jejunum.