Electrogenic ATP-dependent Cl- transport by plasma membrane vesicles from Aplysia intestine

A Cl--stimulated adenosinetriphosphatase (ATPase) activity and an ATP-dependent Cl- transport process were found in Aplysia enterocyte plasma membranes. In an attempt to further elucidate this transport process plasma membrane vesicles from Aplysia enterocytes were prepared utilizing differential centrifugation and sucrose density gradient techniques. Electrogenicity of the ATP-dependent Cl- transport was confirmed in three ways. First, an inwardly directed valinomycin-induced K+ diffusion potential, making the vesicle interior electrically positive, enhanced ATP-driven Cl- uptake compared with vesicles lacking the ionophore. Second, ATP plus Cl- increased intravesicular negativity measured by lipophilic triphenylmethylphosphonium distribution across the vesicular membrane. Third, both vanadate and thiocyanate inhibited the ATP plus Cl--dependent intravesicular negativity. These results are consistent with the hypothesis that the active electrogenic Cl- transport mechanism in Aplysia intestine could be a Cl--stimulated ATPase found in the enterocyte plasma membrane.