RECONSTITUTION OF HUMAN RED-BLOOD-CELL NA H AND NA/NA EXCHANGE TRANSPORT/

Na/H and Na/Na exchange transport was measured using human erythrocyte membrane proteins solubilized with octyl glucoside and reconstituted into voltage clamped soybean phospholipid membrane vesicles, The uptak e of Na in exchange for either H or Na was: 1) 8 to 10 times higher in proteoliposomes that contained erythrocyte proteins than in proteolip osomes that contained heat denatured proteins or in liposomes that con tained no proteins; 2) not affected by ouabain, bumetanide, or 4.4'-di isothiocyanostilbene-2 -2'-disulfonic acid (DIDS); 3) inhibited by ami loride, 5- (n-ethyl-n-isopropyl)amitoride (EIPA), and 5-(n-ethyl-1-n-i sobutyl)amiloride (MIA) but not phenamil; and 4) inhibited by lithium (Li) in a concentration-dependent manner. Incubation of erythrocyte pr oteins with a low concentration of immobilized trypsin resulted in a s ignificant increase (52%) in Na/Na transport, but no change was seen i n Na/H transport. A higher concentration of trypsin increased Na/H tra nsport by more than 2.5 times but did not increase Na/Na transport fur ther. Examination of these studies indicates that, as assayed in recon stituted proteoliposomes that contained erythrocyte proteins, there is a differential response between Na/H and Na/Na transport to trypsin.