Sulfate uptake by crustacean hepatopancreatic brush border membrane vesicles

Purified brush border membrane vesicles (BBMV) were prepared from Atlantic lobster (Homarus americanus) hepatopancreas using differential centrifugation and Mg+2 precipitation techniques. Uptake of 0.1 mM 35SO4-2 was stimulated by pre-loading vesicles with Cl- leading to a transient accumulation of isotope more than twice that at equilibrium. Pre-loading with HCO3- or gluconate had no effect on sulfate uptake. No stimulation of 35SO4-2 was observed in the presence of inwardly directed Na+ or tetramethylammonium+ gradients. Uptake of the divalent anion was strongly stimulated by inwardly directed proton gradients (pHo < pHi) and markedly inhibited by outwardly directed proton gradients (pHo > pHi). 35SO4-2/Cl- exchange was enhanced by imposing a transmembrane inside positive K+ diffusion potential and inhibited by a membrane potential of the opposite polarity (K+/valinomycin). Results suggest the presence of a proton-dependent, electrogenic anion antiport mechanism in BBMV isolated from the crustacean hepatopancreas