ALPHA-MEGLC AND D-GLUCOSE TRANSPORT BY HEPATOPANCREATIC BRUSH-BORDER MEMBRANE-VESICLES FROM PRAWN

Sugar transport by prawn (Penaeus japonicus) hepatopancreatic epitheli um has been studied. Brush-border membrane vesicles (hBBMV) were isola ted, studies of osmotic reactivity were made indicating that these ves icles were closed and with low contamination from basolateral membrane s. Incubation of hBBMV in the presence of Na+ resulted in rapid sugar uptake by the vesicles with an overshoot at 5 min, achieving the equil ibrium value at 60 min. The absence of Na+ or the presence of phloridz in inhibited the overshoot. This uptake appears to be dependent on the membrane potential, since K+ efflux down its concentration gradient i n the presence of valinomycin accelerated sugar influx and increased t he overshoot when K+-loaded hBBMV were used. The kinetic study of Na+- dependent sugar uptake reveals that values of Km and Vmax were of the same order of magnitud as those described for other absorptive epithel ia.