Electroneutral Na1/H1 exchange in brush-border membrane vesicles from Penaeus japonicus hepatopancreas

exchange in brush-border membrane vesicles from Penaeus japonicus hepatopancreas. Am. J. Physiol. 274 (Regulatory Integrative Comp. Physiol. 43): R486–R493, 1998.—An elec-troneutral Na1/H1 exchange mechanism (dimethylamiloride inhibitable, Li1 sensitive, and Ca21 insensitive) was identi-fied in brush-border membrane vesicles (BBMV) from Ku-ruma prawn hepatopancreas by monitoring Na1-dependent H1 fluxes with the pH-sensitive dye acridine orange and measuring 22Na1 uptake. Kinetic parameters measured un-der short-circuited conditions were the Na1 concentration that yielded one-half of the maximal dissipation rate (Fmax) of the preset transmembrane DpH (KNa) 5 15 6 2 mM and Fmax 5 3,626 6 197 DF ·min21 ·mg protein21, with a Hill coefficient for Na1 of,1. In addition, the inhibitory constant for dimethylamiloride was found to be,1 µM. The electroneu